Support token providers in Bearer Auth middleware.

Sources/ASConnectService/Catalogs/ASConnectService.docc/Library.md

@@ -25,6 +25,14 @@ let client = Client(
 )
 ```
 
+Tokens expire after 20 minutes at most. For longer-lived clients, pass a token provider instead, which is called on every request:
+
+```swift
+BearerAuthMiddleware {
+    try await tokenStore.validToken()
+}
+```
+
 ### Making API Calls
 
 The ``Client`` conforms to ``APIProtocol``, which defines a method for every endpoint in the App Store Connect API. Each method accepts an `Input` value and returns an `Output` value with the response.

Sources/ASConnectService/Sources/Public/Middlewares/BearerAuthMiddleware.swift

@@ -13,10 +13,6 @@
 // ===----------------------------------------------------------------------===
 
 import struct Foundation.URL
-import struct Foundation.URLComponents
-import struct Foundation.URLQueryItem
-import struct HTTPTypes.HTTPField
-import struct HTTPTypes.HTTPFields
 import struct HTTPTypes.HTTPRequest
 import struct HTTPTypes.HTTPResponse
 import protocol OpenAPIRuntime.ClientMiddleware
@@ -30,21 +26,43 @@ import class OpenAPIRuntime.HTTPBody
 ///
 /// ## Usage
 ///
+/// Provide a fixed token:
+///
 /// ```swift
 /// let middleware = BearerAuthMiddleware(token: "your-jwt-token")
 /// ```
+///
+/// Tokens expire after 20 minutes at most, so long-lived clients should provide a token provider instead:
+///
+/// ```swift
+/// let middleware = BearerAuthMiddleware {
+///     try await tokenStore.validToken()
+/// }
+/// ```
 public struct BearerAuthMiddleware {
     // MARK: Properties
 
-    /// The Bearer token to include in the `Authorization` header of each request.
-    private let token: String
+    /// The closure that provides the Bearer token for each request.
+    private let tokenProvider: @Sendable () async throws -> String
 
     // MARK: Initializers
 
-    /// Creates a new middleware instance with the given Bearer token.
-    /// - Parameter token: A JSON Web Token (JWT) string used to authenticate requests to the App Store Connect API.
-    init(token: String) {
-        self.token = token
+    /// Creates a new middleware instance with a fixed Bearer token.
+    /// - Parameter token: A JSON Web Token (JWT) used to authenticate requests to the App Store Connect API.
+    public init(
+        token: String
+    ) {
+        self.init { token }
+    }
+
+    /// Creates a new middleware instance that asks for a Bearer token on every request.
+    ///
+    /// If the provider throws, the error is rethrown and the request is not sent.
+    /// - Parameter tokenProvider: A closure that returns a valid JSON Web Token (JWT).
+    public init(
+        tokenProvider: @escaping @Sendable () async throws -> String
+    ) {
+        self.tokenProvider = tokenProvider
     }
 }
 
@@ -68,6 +86,8 @@ extension BearerAuthMiddleware: ClientMiddleware {
         operationID: String,
         next: @Sendable (HTTPRequest, HTTPBody?, URL) async throws -> (HTTPResponse, HTTPBody?)
     ) async throws -> (HTTPResponse, HTTPBody?) {
+        let token = try await tokenProvider()
+
         var request = request
         request.headerFields[.authorization] = "Bearer \(token)"