Support token providers in Bearer Auth middleware.

Tests/ASConnectService/Cases/Public/Middlewares/BearerAuthMiddlewareTests.swift

@@ -3,7 +3,8 @@ import HTTPTypes
 import OpenAPIRuntime
 import Testing
 
-@testable import ASConnectService
+// A non-testable import ensures that the middleware can be created from outside the module.
+import ASConnectService
 
 @Suite("BearerAuthMiddleware")
 struct BearerAuthMiddlewareTests {
@@ -112,6 +113,67 @@ struct BearerAuthMiddlewareTests {
             }
         )
     }
+
+    @Test("Asks the token provider for a token on every request")
+    func asksTokenProviderOnEveryRequest() async throws {
+        let tokens = TokenSequence()
+        let middleware = BearerAuthMiddleware {
+            await tokens.next()
+        }
+
+        for expectedToken in ["token-1", "token-2"] {
+            _ = try await middleware.intercept(
+                .get,
+                body: nil,
+                baseURL: .base,
+                operationID: "listApps",
+                next: { interceptedRequest, _, _ in
+                    #expect(interceptedRequest.headerFields[.authorization] == "Bearer \(expectedToken)")
+
+                    return (HTTPResponse(status: .ok), nil)
+                }
+            )
+        }
+    }
+
+    @Test("Rethrows the token provider error without calling the next handler")
+    func rethrowsTokenProviderError() async throws {
+        let middleware = BearerAuthMiddleware {
+            throw TokenError.expired
+        }
+
+        await #expect(throws: TokenError.expired) {
+            _ = try await middleware.intercept(
+                .get,
+                body: nil,
+                baseURL: .base,
+                operationID: "listApps",
+                next: { _, _, _ in
+                    Issue.record("The next handler should not be called when the token provider throws")
+
+                    return (HTTPResponse(status: .ok), nil)
+                }
+            )
+        }
+    }
+}
+
+// MARK: - Helpers
+
+/// An actor that returns a new token every time it is asked for one.
+private actor TokenSequence {
+    private var count = 0
+
+    func next() -> String {
+        count += 1
+
+        return "token-\(count)"
+    }
+}
+
+/// An error thrown by a token provider.
+private enum TokenError: Error {
+    case expired
 }
 
 // MARK: - HTTPRequest+Samples