Add operation for merging sets to build ID api (#297)

Author: Sushisource

temporal/api/workflowservice/v1/request_response.proto

@@ -1084,6 +1084,13 @@ message UpdateWorkerBuildIdCompatibilityRequest {
         bool make_set_default = 3;
     }
 
+    message MergeSets {
+        // A build ID in the set whose default will become the merged set default
+        string primary_set_build_id = 1;
+        // A build ID in the set which will be merged into the primary set
+        string secondary_set_build_id = 2;
+    }
+
     string namespace = 1;
     // Must be set, the task queue to apply changes to. Because all workers on a given task queue
     // must have the same set of workflow & activity implementations, there is no reason to specify
@@ -1110,6 +1117,12 @@ message UpdateWorkerBuildIdCompatibilityRequest {
         // (-- api-linter: core::0140::prepositions=disabled
         //     aip.dev/not-precedent: Within makes perfect sense here. --)
         string promote_build_id_within_set = 6;
+        // Merge two existing sets together, thus declaring all build IDs in both sets compatible
+        // with one another. The primary set's default will become the default for the merged set.
+        // This is useful if you've accidentally declared a new ID as incompatible you meant to
+        // declare as compatible. The unusual case of incomplete replication during failover could
+        // also result in a split set, which this operation can repair.
+        MergeSets merge_sets = 7;
     }
 }
 message UpdateWorkerBuildIdCompatibilityResponse {