Overhauled the library with several new features (#5)

## Summary

Updates the library to v4.5.1 of the App Store Connect API, and ships it as a breaking 2.0.0 release with pagination, API key authentication, rate limiting, and a lighter install for consumers.

## Breaking changes

- **Minimum platforms:** iOS 14, macOS 11, tvOS 14, watchOS 7, and visionOS 1.
- **Toolchain:** Swift 6.0+ (Xcode 16+). The package builds in the Swift 6 language mode.
- **Runtime:** requires `swift-openapi-runtime` 1.11.0 or later.

## Changes

- **API:** updated the OpenAPI specification to v4.5.1, covering 1,303 operations and 1,473 schemas.
- **Pagination:** the spec patch adds the undocumented `cursor` query parameter to the 465 paged operations. `PagedDocumentLinks.nextCursor` reads the cursor from a page, and `PagedSequence` iterates every page.
- **Authentication:** `APIKeyTokenProvider` signs ES256 tokens from an API key and reuses each one until a minute before it expires. `BearerAuthMiddleware` now accepts a token provider.
- **Rate limiting:** `RateLimitMiddleware` retries `429` responses, waiting for `Retry-After` or backing off exponentially.
- **Generated code:** committed to `Sources/ASConnectService/Sources/Public/Generated` instead of generated by a build plugin. Consumers now resolve 4 packages instead of 12, and Xcode no longer asks to trust a plugin.
- **Tooling:**
  - `make oas-download` now downloads, patches, generates, and checks the docs in one go.
  - New `make oas-generate`, `make oas-validate`, and `make doc-check` targets.
  - The generator is pinned in `Tools/`, and the DocC plugin is only resolved by the documentation targets.
- **Documentation:** the DocC catalog now lists every operation and schema in the spec, and the catalog and README are rewritten for the new APIs.
- **Housekeeping:** Apache 2.0 license headers on every Swift file, including `Package.swift` and the tests.

Reviewed-on: #5
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>

Sources/ASConnectService/Catalogs/ASConnectService.docc/Extensions/Client.md

@@ -1,21 +1,19 @@
 # ``Client``
 
-The API client for performing HTTP operations against the App Store Connect API.
+The App Store Connect API client.
 
 ## Overview
 
-The ``Client`` struct is the main entry point for interacting with the App Store Connect API. It conforms to ``APIProtocol`` and provides concrete implementations for all available API operations.
+``Client`` implements every ``APIProtocol`` method by sending the request through its transport, after passing it through its middlewares.
 
-### Creating a Client
-
-Create a ``Client`` by providing a server URL, a transport, and optionally a list of middlewares for authentication or request customization.
+Include ``BearerAuthMiddleware`` in `middlewares` to authenticate requests:
 
 ```swift
 import ASConnectService
 import OpenAPIURLSession
 
 let client = Client(
-    serverURL: try Servers.server1(),
+    serverURL: try Servers.Server1.url(),
     transport: URLSessionTransport(),
     middlewares: [
         BearerAuthMiddleware(token: yourJWTToken)
@@ -23,12 +21,10 @@ let client = Client(
 )
 ```
 
-### Making API Calls
-
-Each method on the ``Client`` corresponds to an HTTP endpoint defined in the App Store Connect API OpenAPI specification. Methods accept an `Input` value and return an `Output` value representing the response.
+Each method takes either a single `Input` value or its `path`, `query`, `headers`, and `body` as separate arguments:
 
 ```swift
-let response = try await client.appsGetCollection(.init())
+let response = try await client.appsGetInstance(path: .init(id: appID))
 ```
 
 ## Topics