refactor: reload theme.yaml when theme reload (#2486)

#### What type of PR is this?
/kind improvement
/area core
/milestone 2.0

#### What this PR does / why we need it:
主题 reload endpoint 增加对 theme.yaml 的 reload 操作
#### Which issue(s) this PR fixes:

Fixes #

#### Special notes for your reviewer:
/cc @halo-dev/sig-halo 
#### Does this PR introduce a user-facing change?

```release-note
None
```

src/main/java/run/halo/app/core/extension/endpoint/ThemeEndpoint.java

@@ -53,6 +53,7 @@ import run.halo.app.infra.properties.HaloProperties;
 import run.halo.app.infra.utils.DataBufferUtils;
 import run.halo.app.infra.utils.FileUtils;
 import run.halo.app.infra.utils.YamlUnstructuredLoader;
+import run.halo.app.theme.ThemePathPolicy;
 
 /**
  * Endpoint for managing themes.
@@ -66,10 +67,12 @@ public class ThemeEndpoint implements CustomEndpoint {
 
     private final ReactiveExtensionClient client;
     private final HaloProperties haloProperties;
+    private final ThemePathPolicy themePathPolicy;
 
     public ThemeEndpoint(ReactiveExtensionClient client, HaloProperties haloProperties) {
         this.client = client;
         this.haloProperties = haloProperties;
+        this.themePathPolicy = new ThemePathPolicy(haloProperties.getWorkDir());
     }
 
     @Override
@@ -101,7 +104,7 @@ public class ThemeEndpoint implements CustomEndpoint {
                         .implementation(String.class)
                     )
                     .response(responseBuilder()
-                        .implementation(Setting.class))
+                        .implementation(Theme.class))
             )
             .build();
     }
@@ -124,12 +127,26 @@ public class ThemeEndpoint implements CustomEndpoint {
                             persistent.setSpec(setting.getSpec());
                             return client.update(persistent);
                         })
-                        .switchIfEmpty(Mono.defer(() -> client.create(setting))))
+                        .switchIfEmpty(Mono.defer(() -> client.create(setting)))
-                    .orElse(Mono.empty());
+                        .thenReturn(theme)
+                    )
+                    .orElse(Mono.just(theme));
             })
-            .flatMap(setting -> ServerResponse.ok()
+            .flatMap(themeToUse -> {
+                Path themePath = themePathPolicy.generate(themeToUse);
+                Path themeManifestPath = ThemeUtils.resolveThemeManifest(themePath);
+                if (themeManifestPath == null) {
+                    return Mono.error(new IllegalArgumentException(
+                        "The manifest file [theme.yaml] is required."));
+                }
+                Unstructured unstructured = ThemeUtils.loadThemeManifest(themeManifestPath);
+                Theme newTheme = Unstructured.OBJECT_MAPPER.convertValue(unstructured, Theme.class);
+                themeToUse.setSpec(newTheme.getSpec());
+                return client.update(themeToUse);
+            })
+            .flatMap(theme -> ServerResponse.ok()
                 .contentType(MediaType.APPLICATION_JSON)
-                .bodyValue(setting));
+                .bodyValue(theme));
     }
 
     public record InstallRequest(
@@ -299,7 +316,7 @@ public class ThemeEndpoint implements CustomEndpoint {
             }
         }
 
-        private static Unstructured loadThemeManifest(Path themeManifestPath) {
+        static Unstructured loadThemeManifest(Path themeManifestPath) {
             List<Unstructured> unstructureds =
                 new YamlUnstructuredLoader(new FileSystemResource(themeManifestPath))
                     .load();

src/test/java/run/halo/app/core/extension/endpoint/ThemeEndpointTest.java

@@ -30,6 +30,7 @@ import org.springframework.web.reactive.function.BodyInserters;
 import reactor.core.publisher.Mono;
 import run.halo.app.core.extension.Setting;
 import run.halo.app.core.extension.Theme;
+import run.halo.app.extension.AbstractExtension;
 import run.halo.app.extension.Metadata;
 import run.halo.app.extension.ReactiveExtensionClient;
 import run.halo.app.extension.Unstructured;
@@ -61,11 +62,10 @@ class ThemeEndpointTest {
     @BeforeEach
     void setUp() throws IOException {
         tmpHaloWorkDir = Files.createTempDirectory("halo-unit-test");
+        when(haloProperties.getWorkDir()).thenReturn(tmpHaloWorkDir);
 
         ThemeEndpoint themeEndpoint = new ThemeEndpoint(extensionClient, haloProperties);
 
-        when(haloProperties.getWorkDir()).thenReturn(tmpHaloWorkDir);
-
         defaultTheme = ResourceUtils.getFile("classpath:themes/test-theme.zip");
 
         webTestClient = WebTestClient
@@ -122,6 +122,7 @@ class ThemeEndpointTest {
         theme.setMetadata(new Metadata());
         theme.getMetadata().setName("fake-theme");
         theme.setSpec(new Theme.ThemeSpec());
+        theme.getSpec().setDisplayName("Hello");
         theme.getSpec().setSettingName("fake-setting");
         when(extensionClient.fetch(Theme.class, "fake-theme"))
             .thenReturn(Mono.just(theme));
@@ -152,9 +153,20 @@ class ThemeEndpointTest {
                       children: Register
             """);
 
+        Files.writeString(themeWorkDir.resolve("theme.yaml"), """
+            apiVersion: v1alpha1
+            kind: Theme
+            metadata:
+              name: fake-theme
+            spec:
+              displayName: Fake Theme
+            """);
+        when(extensionClient.update(any(Theme.class)))
+            .thenReturn(Mono.just(theme));
+
         when(extensionClient.update(any(Setting.class)))
             .thenReturn(Mono.just(setting));
-        ArgumentCaptor<Setting> captor = ArgumentCaptor.forClass(Setting.class);
+        ArgumentCaptor<AbstractExtension> captor = ArgumentCaptor.forClass(Setting.class);
         webTestClient.put()
             .uri("/themes/fake-theme/reload-setting")
             .exchange()
@@ -162,10 +174,12 @@ class ThemeEndpointTest {
             .isOk()
             .expectBody(Setting.class)
             .value(settingRes -> {
-                verify(extensionClient, times(1)).update(captor.capture());
+                verify(extensionClient, times(2)).update(captor.capture());
                 verify(extensionClient, times(0)).create(any(Setting.class));
-                Setting value = captor.getValue();
+                List<AbstractExtension> allValues = captor.getAllValues();
-                System.out.println(JsonUtils.objectToJson(value));
+                assertThat(allValues.get(0)).isInstanceOfAny(Setting.class);
+                Setting newSetting = (Setting) allValues.get(0);
+                Theme newTheme = (Theme) allValues.get(1);
                 try {
                     JSONAssert.assertEquals("""
                             {
@@ -188,7 +202,24 @@ class ThemeEndpointTest {
                                "metadata": {}
                              }
                             """,
-                        JsonUtils.objectToJson(value),
+                        JsonUtils.objectToJson(newSetting),
+                        true);
+
+                    JSONAssert.assertEquals("""
+                            {
+                                "spec": {
+                                    "displayName": "Fake Theme",
+                                    "version": "*",
+                                    "require": "*"
+                                },
+                                "apiVersion": "theme.halo.run/v1alpha1",
+                                "kind": "Theme",
+                                "metadata": {
+                                    "name": "fake-theme"
+                                }
+                            }
+                            """,
+                        JsonUtils.objectToJson(newTheme),
                         true);
                 } catch (JSONException e) {
                     throw new RuntimeException(e);