fix: Discovery Document metadata handling causes PKCE to be disabled for Entra ID (CIAM)

[Kronusus]

Description

I encountered an issue where authentication with Microsoft Entra ID (CIAM) fails with AADSTS9002325: Proof Key for Code Exchange is required. This happens because the Entra ID discovery document does not publish the code_challenge_methods_supported property, even though PKCE is required for SPA clients. The oidc package correctly parses the metadata, sees the missing field, and presumably defaults to not sending the code_challenge.

Workaround: Manually constructing OidcProviderMetadata and explicitly adding the missing field fixes the issue:

discoveryDocument: OidcProviderMetadata.fromJson({
// ... other fields from .well-known/openid-configuration
"code_challenge_methods_supported": ["S256"], // FORCE PKCE SUPPORT
}),

[ahmednfwela]

this is a known issue, and is the reason we have discovery document overrides