Fix the problem of being able to configure invalid external URL (#6840)

#### What type of PR is this?

/kind bug
/area core
/milestone 2.20.x

#### What this PR does / why we need it:

This PR makes users not be able to configure a invalid external URL like `https:www/halo.run` even if it is an valid URL format.

#### Which issue(s) this PR fixes:

Fixes #6837 

#### Does this PR introduce a user-facing change?

```release-note
修复可配置无效的外部访问地址的问题
```

application/src/main/java/run/halo/app/infra/properties/HaloProperties.java

@@ -2,6 +2,7 @@ package run.halo.app.infra.properties;
 
 import jakarta.validation.Valid;
 import jakarta.validation.constraints.NotNull;
+import java.net.URISyntaxException;
 import java.net.URL;
 import java.nio.file.Path;
 import java.util.HashSet;
@@ -69,9 +70,26 @@ public class HaloProperties implements Validator {
     @Override
     public void validate(Object target, Errors errors) {
         var props = (HaloProperties) target;
-        if (props.isUseAbsolutePermalink() && props.getExternalUrl() == null) {
+        var externalUrl = props.getExternalUrl();
+        if (props.isUseAbsolutePermalink() && externalUrl == null) {
             errors.rejectValue("externalUrl", "external-url.required.when-using-absolute-permalink",
                 "External URL is required when property `use-absolute-permalink` is set to true.");
         }
+        // check if the external URL is a http or https URL and is not an opaque URL.
+        if (externalUrl != null && !isValidExternalUrl(externalUrl)) {
+            errors.rejectValue("externalUrl", "external-url.invalid-format",
+                "External URL must be a http or https URL.");
+        }
+    }
+
+    private boolean isValidExternalUrl(URL externalUrl) {
+        try {
+            var uri = externalUrl.toURI();
+            return !uri.isOpaque()
+                && uri.getAuthority() != null
+                && Set.of("http", "https").contains(uri.getScheme());
+        } catch (URISyntaxException e) {
+            return false;
+        }
     }
 }

application/src/test/java/run/halo/app/PathPrefixPredicateTest.java

@@ -2,6 +2,7 @@ package run.halo.app;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
+import java.net.URI;
 import org.junit.jupiter.api.Test;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
@@ -34,4 +35,10 @@ public class PathPrefixPredicateTest {
 
     }
 
+
+    @Test
+    void urlTest() {
+        URI uri = URI.create("https:///path");
+        System.out.println(uri);
+    }
 }

application/src/test/java/run/halo/app/infra/properties/HaloPropertiesTest.java

@@ -0,0 +1,45 @@
+package run.halo.app.infra.properties;
+
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.springframework.validation.SimpleErrors;
+
+class HaloPropertiesTest {
+
+    static Stream<Arguments> validateTest() throws MalformedURLException {
+        return Stream.of(
+            Arguments.of(true, new URL("http://localhost:8080"), true),
+            Arguments.of(false, new URL("http://localhost:8080"), true),
+            Arguments.of(true, new URL("https://localhost:8080"), true),
+            Arguments.of(false, new URL("https://localhost:8080"), true),
+            Arguments.of(true, new URL("ftp://localhost:8080"), false),
+            Arguments.of(false, new URL("ftp://localhost:8080"), false),
+            Arguments.of(true, new URL("http:www/halo/run"), false),
+            Arguments.of(false, new URL("http:www/halo.run"), false),
+            Arguments.of(true, new URL("https:www/halo/run"), false),
+            Arguments.of(false, new URL("https:www/halo/run"), false),
+            Arguments.of(true, new URL("https:///path"), false),
+            Arguments.of(false, new URL("https:///path"), false),
+            Arguments.of(true, new URL("http:///path"), false),
+            Arguments.of(false, new URL("http:///path"), false),
+            Arguments.of(true, null, false),
+            Arguments.of(false, null, true)
+        );
+    }
+
+    @ParameterizedTest
+    @MethodSource
+    void validateTest(boolean useAbsolutePermalink, URL externalUrl, boolean valid) {
+        var properties = new HaloProperties();
+        properties.setUseAbsolutePermalink(useAbsolutePermalink);
+        properties.setExternalUrl(externalUrl);
+        var errors = new SimpleErrors(properties);
+        properties.validate(properties, errors);
+        Assertions.assertEquals(valid, !errors.hasErrors());
+    }
+}