Consider updating the XML documentation to discourage using client secrets when possible

[kevinchalet]

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Describe the solution you'd like

With #2417 merged, the OpenIddict server stack now offers 3 standard client authentication methods that all provide a higher level of security compared to client secrets:

• tls_client_auth
• self_signed_tls_client
• private_key_jwt

As such, I'm considering updating the XML documentation to encourage developers to prefer these safer methods when possible.

Additional context

No response