Add OAuth2 FileTokenStorage and OAuth2Manager with tests (#85)

- Implemented `FileTokenStorage` for managing OAuth2 token data using
file storage, including methods for saving, loading, and clearing
tokens.
- Developed `OAuth2Manager` to handle OAuth2 authentication flow,
including token retrieval and refresh logic.
- Added comprehensive unit tests for both `FileTokenStorage` and
`OAuth2Manager` to ensure functionality and error handling.
- Introduced type definitions for `TokenData`, `TokenStorageProvider`,
and `OAuth2Config` to enhance type safety and clarity.

These changes establish a robust foundation for OAuth2 integration,
improving token management and authentication processes in the
application.

Author: anatolyshipitz

workers/main/package-lock.json

@@ -11,6 +11,7 @@
     "@eslint/js": "9.27.0",
     "@temporalio/testing": "1.11.8",
     "@types/node": "22.15.21",
+    "@types/simple-oauth2": "5.0.7",
     "@vitest/coverage-v8": "3.1.3",
     "c8": "10.1.3",
     "dotenv": "16.5.0",
@@ -40,6 +41,7 @@
     "axios-retry": "4.5.0",
     "mongoose": "8.15.1",
     "mysql2": "3.14.1",
+    "simple-oauth2": "5.1.0",
     "zod": "3.25.17"
   }
 }