V0.12.x (#215)

* fix #203 NetworkTransport race, with main-isolated variables (#206)

Co-authored-by: wti <wti@users.noreply.github.com>

* feat/auth: Authentication implementation (#205)

* feat: added authentication

* feat(auth): improvement to error handling

* feat(auth): updated errors and tests in OAuthClientRegistrar

* feat(auth): updated ci conformance package version

* feat(auth): bumped node version

* feat(auth): updated ci conformance step

* feat(auth): improvement to Linux support

* chore: added docc plugin

* chore: added spi yml

* chore: added documentation step to ci

* chore: increased timeout for test from 5 to 10m

---------

Co-authored-by: Paal Øye-Strømme <paal.o.eye@gmail.com>
Co-authored-by: wti <wti@users.noreply.github.com>
Co-authored-by: yehorsobko <yehorsobko@macpaw.com>

Sources/MCP/Base/Authorization/OAuthTokenEndpointClient.swift

@@ -0,0 +1,90 @@
+import Foundation
+
+#if canImport(FoundationNetworking)
+    import FoundationNetworking
+#endif
+
+/// Internal protocol for making OAuth token endpoint requests.
+protocol OAuthTokenRequesting: Sendable {
+    func request(
+        parameters: inout [String: String],
+        endpoint: URL,
+        authentication: OAuthConfiguration.TokenEndpointAuthentication,
+        session: URLSession
+    ) async throws -> OAuthTokenResponse
+}
+
+/// Stateless OAuth token endpoint HTTP client.
+///
+/// Handles the low-level HTTP mechanics of making token requests.
+struct OAuthTokenEndpointClient: Sendable {
+    let urlValidator: OAuthURLValidator
+
+    init(urlValidator: OAuthURLValidator) {
+        self.urlValidator = urlValidator
+    }
+
+    /// Makes a token request to the given endpoint.
+    func request(
+        parameters: inout [String: String],
+        endpoint: URL,
+        authentication: OAuthConfiguration.TokenEndpointAuthentication,
+        session: URLSession
+    ) async throws -> OAuthTokenResponse {
+        var urlRequest = URLRequest(url: endpoint)
+        urlRequest.httpMethod = "POST"
+        urlRequest.setValue(ContentType.formURLEncoded, forHTTPHeaderField: HTTPHeaderName.contentType)
+        urlRequest.setValue(ContentType.json, forHTTPHeaderField: HTTPHeaderName.accept)
+
+        try await authentication.apply(
+            to: &urlRequest,
+            bodyParameters: &parameters,
+            tokenEndpoint: endpoint
+        )
+        urlRequest.httpBody = encodeForm(parameters)
+
+        let (data, response) = try await session.data(for: urlRequest)
+        guard let httpResponse = response as? HTTPURLResponse else {
+            throw OAuthAuthorizationError.tokenRequestFailed(statusCode: -1, oauthError: nil)
+        }
+
+        guard (200..<300).contains(httpResponse.statusCode) else {
+            let oauthError =
+                (try? JSONDecoder().decode(OAuthTokenErrorResponse.self, from: data))?.error
+            throw OAuthAuthorizationError.tokenRequestFailed(
+                statusCode: httpResponse.statusCode,
+                oauthError: oauthError
+            )
+        }
+
+        let decoded = try JSONDecoder().decode(OAuthTokenResponse.self, from: data)
+        guard !decoded.accessToken.isEmpty else {
+            throw OAuthAuthorizationError.tokenResponseInvalid
+        }
+        let tokenType = decoded.tokenType.trimmingCharacters(in: .whitespacesAndNewlines)
+        guard !tokenType.isEmpty,
+            tokenType.caseInsensitiveCompare(OAuthTokenType.bearer) == .orderedSame
+        else {
+            throw OAuthAuthorizationError.tokenResponseInvalid
+        }
+        return decoded
+    }
+
+    private func encodeForm(_ params: [String: String]) -> Data {
+        let body = params
+            .sorted { $0.key < $1.key }
+            .map { key, value in "\(percentEncode(key))=\(percentEncode(value))" }
+            .joined(separator: "&")
+        return Data(body.utf8)
+    }
+
+    private func percentEncode(_ string: String) -> String {
+        let allowed = CharacterSet(
+            charactersIn:
+                "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~"
+        )
+        return string.addingPercentEncoding(withAllowedCharacters: allowed) ?? string
+    }
+}
+
+extension OAuthTokenEndpointClient: OAuthTokenRequesting {}