refactor(connector): [Klarna] Refactor Authorize call and configs for prod (#4750)

Co-authored-by: Samraat Bansal <samraat.bansal@juspay.in>
Files to modify:


**common_config.rs**
  Add:
    - enum: pub::KlarnaEndpoint

**connector.rs**
  Add:
    - enum: pub::KlarnaEndpoint

**response_modifier.rs**
  Modify existing code

**transformer.rs**
  Modify existing code

**klarna.rs**
  Remove:
    - impl: impl ConnectorValidation for Klarna
  Add:
    - function: private::validate_capture_method
    - function: private::build_region_specific_endpoint
    - impl: impl ConnectorValidation for Klarna

**transformers.rs**
  Add:
    - function: private::from
    - function: private::try_from
    - struct: pub::KlarnaConnectorMetadataObject
    - enum: pub::KlarnaEndpoint
    - impl: impl From<KlarnaEndpoint> for String
    - impl: impl TryFrom<&Option<pii::SecretSerdeValue>> for KlarnaConnectorMetadataObject

**admin.rs**
  Modify existing code