Retrieve user auth provider additional details

PR-Codex overview

This PR focuses on updating the OAuth implementation in the InAppWallet class and adding a method to retrieve user authentication details.

Detailed summary

• Changed the OAuth provider from AuthProvider.Steam to AuthProvider.Github in Program.cs.
• Added the GetUserAuthDetails method in EcosystemWallet.cs to fetch user authentication details.
• Introduced a private static method Base64UrlDecode to decode JWT tokens.

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