fix(connector): [NEXIXPAY] Add Validation Checks for Request Fields (#8345)

Co-authored-by: Sayak Bhattacharya <sayak.b@Sayak-Bhattacharya-G092THXJ34.local>

crates/hyperswitch_interfaces/src/errors.rs

@@ -127,6 +127,13 @@ pub enum ConnectorError {
     },
     #[error("Field {fields} doesn't match with the ones used during mandate creation")]
     MandatePaymentDataMismatch { fields: String },
+    #[error("Field '{field_name}' is too long for connector '{connector}'")]
+    MaxFieldLengthViolated {
+        connector: String,
+        field_name: String,
+        max_length: usize,
+        received_length: usize,
+    },
 }
 
 impl ConnectorError {