feat: Support Regex validation for custom attributes (#7856)

This allows a user to add/update a custom regex and a cue while defining custom attributes(Only applicable for type- text).
While adding/editing custom attributes, the values are validated against the attribute definition regex, and if it is incorrect, a cue message or default error message is shown and restricts invalid values from being saved.

Fixes: #6866

app/controllers/api/v1/accounts/custom_attribute_definitions_controller.rb

@@ -39,6 +39,8 @@ class Api::V1::Accounts::CustomAttributeDefinitionsController < Api::V1::Account
       :attribute_display_type,
       :attribute_key,
       :attribute_model,
+      :regex_pattern,
+      :regex_cue,
       attribute_values: []
     )
   end