Sign out when token can't be refreshed

Author: darrarski

Sources/DropboxClient/Auth.swift

@@ -213,6 +213,7 @@ extension Auth {
         let statusCode = (response as? HTTPURLResponse)?.statusCode
 
         guard let statusCode, (200..<300).contains(statusCode) else {
+          await saveCredentials(nil)
           throw Error.response(statusCode: statusCode, data: responseData)
         }
 

Tests/DropboxClientTests/AuthTests.swift

@@ -392,6 +392,7 @@ final class AuthTests: XCTestCase {
         var keychain = Keychain.unimplemented()
         keychain.loadCredentials = { await credentials.value }
         keychain.saveCredentials = { await credentials.setValue($0) }
+        keychain.deleteCredentials = { await credentials.setValue(nil) }
         return keychain
       }(),
       httpClient: .init { _ in
@@ -423,6 +424,9 @@ final class AuthTests: XCTestCase {
         "Expected to throw response error, got \(error)"
       )
     }
+    await credentials.withValue {
+      XCTAssertNil($0)
+    }
   }
 
   func testSignOut() async {