Allow keypay_api to overwrite member's fields in keypay with blank values
Allow keypay_api to overwrite member's fields in keypay with blank values

Background: Currently, even some field of member value is nil or empty, it will keep the original value in keypay when we syncing. The reason is that keypay's rule uses signal "clear" to notify that we want to overwrite that fields with blank values, otherwise it will keep the original values.

Trello reference link: https://trello.com/c/cmBn7ycG/1172-p2-blank-fields-in-e-f-does-not-blank-the-field-in-kp
Thinkei/keypay-integration,Thinkei/keypay-integration