Function validateCredentialOffer

Validates a credential offer against IT-Wallet specifications for the configured version.

Required validations (all versions):

• credential_issuer must be an HTTPS URL
• credential_configuration_ids must contain at least one identifier
• grants object is REQUIRED
• authorization_code grant is REQUIRED (pre-authorized code is NOT supported)

Version-specific validations:

• v1.3: scope is REQUIRED within the authorization_code grant
• v1.4: the credential offer no longer carries a scope

Conditional validations:

• authorization_server is REQUIRED when the Credential Issuer uses multiple Authorization Servers
• If authorization_server is present, it MUST match one of the servers in the Credential Issuer metadata