feat: add documentation crate and integrate OpenAPI specifications

- Added a new crate `doc` for API documentation.
- Integrated `utoipa` for OpenAPI support in the presentation layer.
- Updated routes to include social features (follow, unfollow, etc.) and diary export.
- Enhanced API request and response structures with new DTOs for social interactions.
- Updated `Cargo.toml` files to include new dependencies and features.
- Modified Dockerfile to copy the new documentation crate.
- Refactored existing handlers and routes to accommodate new API endpoints.
- Updated tests to cover new functionality and ensure proper API behavior.

crates/doc/src/lib.rs

@@ -0,0 +1,16 @@
+use axum::Router;
+use utoipa::openapi::OpenApi;
+use utoipa_scalar::{Scalar, Servable};
+use utoipa_swagger_ui::SwaggerUi;
+
+pub trait ApiDocExt {
+    fn with_api_doc(self, spec: OpenApi) -> Self;
+}
+
+impl ApiDocExt for Router {
+    fn with_api_doc(self, spec: OpenApi) -> Self {
+        tracing::info!("API docs at /docs (Swagger) and /scalar");
+        self.merge(SwaggerUi::new("/docs").url("/openapi.json", spec.clone()))
+            .merge(Scalar::with_url("/scalar", spec))
+    }
+}