Fix : token_endpoint_auth_signing_alg_values_supported is a json array

[yannj-fr]

Motivation and Context

Fixes the OAuthMetadata model validated by Pydantic, token_endpoint_auth_signing_alg_values_supported has to be a list of string, or validation would fail

How Has This Been Tested?

Tested against an Auth0 oauth implementation

Breaking Changes

No

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

[Kludex]

There are two others that the type is analogously wrong. Can you fix it?

Also, what are the possible values of it?

[yannj-fr]

fixed accordingly and updates the possible values.
I have been checking the rest for consistency