### Description
This PR integrates the **`utoipa`** and **`utoipa-redoc`** crates to automatically generate OpenAPI-compliant API documentation for the backend project.
#### Overview
To improve development efficiency and API maintainability, this change introduces `utoipa` to automate the API documentation process. By adding specific attribute macros to the source code, we can generate detailed API specifications directly and serve them through an interactive UI provided by `utoipa-redoc`.
#### Key Changes
* **Dependencies Added**
* Added `utoipa`, `utoipa-gen`, and `utoipa-redoc` to `Cargo.toml`.
* `utoipa` is used to define OpenAPI objects.
* `utoipa-redoc` is used to serve the ReDoc documentation UI.
* **Code Refactoring**
* **HTTP handler logic** in each feature (`auth`, `image`, `post`) has been extracted from the `..._web_routes.rs` files into their own dedicated files (e.g., `get_post_by_id_handler.rs`). This makes the code structure cleaner and simplifies adding documentation attributes to each handler.
* Renamed the `PostController` method from `get_full_post` to `get_post_by_id` for a more RESTful-compliant naming convention.
* **API Doc Annotation**
* Added `#[derive(ToSchema)]` or `#[derive(IntoParams)]` to all DTOs (Data Transfer Objects) so they can be recognized by `utoipa` to generate the corresponding schemas.
* Added the `#[utoipa::path]` macro to all HTTP handler functions, describing the API's path, HTTP method, tags, summary, expected responses, and security settings.
* **Doc Aggregation & Serving**
* Added an `..._api_doc.rs` file in each feature module to aggregate all API paths within that module.
* Added a new `api_doc.rs` file in the `server` crate to merge the OpenAPI documents from all features, set global information (like title, version, and the OAuth2 security scheme), and serve the documentation page on the `/redoc` route using `Redoc::with_url`.
### Package Changes
```toml
utoipa = { version = "5.4.0", features = ["actix_extras"] }
utoipa-redoc = { version = "6.0.0", features = ["actix-web"] }
```
### Screenshots
### Reference
Resolves#103
### Checklist
- [x] A milestone is set
- [x] The related issuse has been linked to this branch
Reviewed-on: #106
Co-authored-by: SquidSpirit <squid@squidspirit.com>
Co-committed-by: SquidSpirit <squid@squidspirit.com>
### Description
- Add some endpoints about image:
- POST `/image/upload`
- GET `/image/{id}`
> [!NOTE]
> Since there isn't identity authentication, the `/image` endpoints should be restricted to private network in nginx.
> [!NOTE]
> Volume for backend should be configured in `pod.yaml`.
### Package Changes
```toml
actix-multipart = "0.7.2"
```
### Screenshots
_No response_
### Reference
Resolves#78
### Checklist
- [x] A milestone is set
- [x] The related issuse has been linked to this branch
Reviewed-on: #84
Co-authored-by: SquidSpirit <squid@squidspirit.com>
Co-committed-by: SquidSpirit <squid@squidspirit.com>
