Constant API_KEY_SUBMIT_CHANGE 

pub const API_KEY_SUBMIT_CHANGE: i16 = _; // 1_003i16

Forwards a Controller::submit_change from a follower to the leader.

The body is the wincode-encoded Vec<MetadataRecord>. The response carries a single error_code, where 0 means applied and any non-zero value means not-leader or metadata-validation.