Adapt to reference implementation

[alexbalakirev]

• Add FAPI URL and BAPI URL to config
• Extend "/v2" to BAPI URL before usage (so you pass it without it in config)
• Adapt issuer validation, see https://github.com/corbado/corbado-go/blob/main/internal/services/session/session.go#L138
• Change short-term session naming to session-token naming (see Renamed short-term session to session-token corbado-go#39)
• Change cbo_short_session to cbo_session_token (see Renamed short-term session to session-token corbado-go#39)
• Do a major release (bump major version because the changes are not backwards-compatible)
• TODO für Stefan checken ob validateToken() noch verbessern müssen (Exception throwen plus Errorcodes plus Unittests für jeden Errorcode)
• Remove session_service.get_and_validate_short_session_value() and session_service.get_current_user() and introduce validate_token()
• Throw exceptions if the session-token (JWT) is invalid and provide some error codes like in Go, see here: https://github.com/corbado/corbado-go/blob/main/pkg/validationerror/code.go (we decided to go for exceptions here because we found out its harder to ignore :))
• Implement unit tests for validate_token() (see https://github.com/corbado/corbado-go/blob/main/tests/unit/session/session_test.go, copy all of them)

[alexbalakirev]

@corbadoman Ready for review. To make a deployment for the new version I need CORBADO_FRONTEND_API secret. After that I could update the example applications if needed.