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>

Tests/ASConnectService/Cases/Public/Extensions/PagedDocumentLinksTests.swift

@@ -0,0 +1,65 @@
+// ===----------------------------------------------------------------------===
+//
+// This source file is part of the ASConnectService open source project
+//
+// Copyright (c) 2026 Röck+Cöde VoF. and the ASConnectService project authors
+// Licensed under Apache license v2.0
+//
+// See LICENSE for license information
+// See CONTRIBUTORS for the list of ASConnectService project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// ===----------------------------------------------------------------------===
+
+import Testing
+
+// A non-testable import ensures that the extension can be used from outside the module.
+import ASConnectService
+
+@Suite("PagedDocumentLinks")
+struct PagedDocumentLinksTests {
+    // MARK: Tests
+
+    @Test("Returns the cursor from the next link")
+    func returnsNextCursor() {
+        let links = Components.Schemas.PagedDocumentLinks(
+            _self: .Link.current,
+            next: "https://api.appstoreconnect.apple.com/v1/apps?cursor=Mg.ANmP3sY&limit=2"
+        )
+
+        #expect(links.nextCursor == "Mg.ANmP3sY")
+    }
+
+    @Test("Returns nil when there is no next link")
+    func returnsNilWithoutNextLink() {
+        let links = Components.Schemas.PagedDocumentLinks(_self: .Link.current)
+
+        #expect(links.nextCursor == nil)
+    }
+
+    @Test("Returns nil when the next link has no cursor")
+    func returnsNilWithoutCursor() {
+        let links = Components.Schemas.PagedDocumentLinks(
+            _self: .Link.current,
+            next: "https://api.appstoreconnect.apple.com/v1/apps?limit=2"
+        )
+
+        #expect(links.nextCursor == nil)
+    }
+
+    @Test("Passes the cursor to the query of a paged operation")
+    func passesCursorToQuery() {
+        let query = Operations.AppsGetCollection.Input.Query(limit: 2, cursor: "Mg.ANmP3sY")
+
+        #expect(query.cursor == "Mg.ANmP3sY")
+    }
+}
+
+// MARK: - String+Samples
+
+private extension String {
+    enum Link {
+        static let current: String = "https://api.appstoreconnect.apple.com/v1/apps?limit=2"
+    }
+}