refactor: optimize user creation (#6480)

#### What type of PR is this?
/kind improvement
/area core
/milestone 2.19.x

#### What this PR does / why we need it:
优化用户创建

#### Does this PR introduce a user-facing change?
```release-note
None
```

application/src/main/java/run/halo/app/core/extension/endpoint/UserEndpoint.java

@@ -444,13 +444,9 @@ public class UserEndpoint implements CustomEndpoint {
             })
             .flatMap(userRequest -> {
                 User newUser = CreateUserRequest.from(userRequest);
-                return userService.createUser(newUser, userRequest.roles())
-                    .then(Mono.defer(() -> userService.updateWithRawPassword(userRequest.name(),
-                            userRequest.password()))
-                        .retryWhen(Retry.backoff(5, Duration.ofMillis(100))
-                            .filter(OptimisticLockingFailureException.class::isInstance)
-                        )
-                    );
+                var encryptedPwd = userService.encryptPassword(userRequest.password());
+                newUser.getSpec().setPassword(encryptedPwd);
+                return userService.createUser(newUser, userRequest.roles());
             })
             .flatMap(user -> ServerResponse.ok()
                 .contentType(MediaType.APPLICATION_JSON)

application/src/main/java/run/halo/app/core/extension/service/UserService.java

@@ -27,4 +27,6 @@ public interface UserService {
     Mono<Boolean> confirmPassword(String username, String rawPassword);
 
     Flux<User> listByEmail(String email);
+
+    String encryptPassword(String rawPassword);
 }

application/src/main/java/run/halo/app/core/extension/service/UserServiceImpl.java

@@ -213,6 +213,11 @@ public class UserServiceImpl implements UserService {
         );
     }
 
+    @Override
+    public String encryptPassword(String rawPassword) {
+        return passwordEncoder.encode(rawPassword);
+    }
+
     void publishPasswordChangedEvent(String username) {
         eventPublisher.publishEvent(new PasswordChangedEvent(this, username));
     }