feat: Implement WebFinger discovery and ActivityPub user actor endpoint

- Added a new router for handling well-known endpoints, specifically WebFinger.
- Implemented the `webfinger` function to respond to WebFinger queries.
- Created a new route for WebFinger in the router.
- Refactored user retrieval logic to support both user ID and username in a single endpoint.
- Updated user router to use the new `get_user_by_param` function.
- Added tests for WebFinger discovery and ActivityPub user actor endpoint.
- Updated dependencies in Cargo.toml files to include necessary libraries.

thoughts-backend/api/Cargo.toml

@@ -22,6 +22,8 @@ tower-http = { version = "0.6.6", features = ["fs", "cors"] }
 tower-cookies = "0.11.0"
 anyhow = "1.0.98"
 dotenvy = "0.15.7"
+activitypub_federation = "0.6.5"
+url = "2.5.7"
 
 # db
 sea-orm = { workspace = true }
@@ -29,8 +31,11 @@ sea-orm = { workspace = true }
 # doc
 utoipa = { workspace = true }
 
+serde_json = { workspace = true }
+
 # local dependencies
 app = { path = "../app" }
 models = { path = "../models" }
 
+
 [dev-dependencies]