Phased migrations shouldn't have missing links

Issue Summary

Yes

Steps to Reproduce

1. Migrate from server to cloud in phases. 
2. If both the projects are not present in cloud, then the link will not be migrated from server to cloud. (remote links in Jira)

Expected Results

For this suggestion/feature request , it is expected and requested that for projects where both end points haven't been migrated together the links should still be migrated and should point to server. 

In latter phases the links should get become local links . For a detailed example

• We have links from a issue ABC-1 (On server ) to WER-1 (On Server) and OPU-1 (On Server).
• We want to migrate only ABC and WER projects in first phase keeping OPU on server.
• So post migration we have ABC (On Cloud) , WER (On Cloud) and OPU (On Server).
• What will happen at this stage is ABC-1 (On Cloud) will be linked fine to (WER-1) on cloud, but the link between ABC-1 (On Cloud) and OPU-1(On Server) is lost because of the missing dependency. A link is only migrated when both end points exist. Whenever in future we migrate OPU, the link will come over. 
• What this case is asking is ABC-1 (On Cloud) is linked to WER-1 (On Cloud) and also to (OPU-1) on server after phase 1. 
• Then later in Phase 2 when the OPU project is migrated, we want the remote link to now be converted into a local link as all projects are in cloud. 

Actual Results

Links aren't migrated if both endpoints are available on cloud. 

Workaround

The only possibility currently is waiting till all phases of a migration are complete and then contact atlassian support for help fixing link.