Add documentation on how to migrate an API from test to prod

After copying the Terms API from test to prod using WSO2's CLI took, I figured that the process was involved enough to warrant documentation to easy repeatability.

In order to do a migration, you need to have the password, but I wasn't sure how to address that issue. See here: https://git.doit.wisc.edu/interop/portal/merge_requests/new/diffs?merge_request%5Bsource_branch%5D=migrate-an-api-docs&merge_request%5Bsource_project_id%5D=7656&merge_request%5Btarget_branch%5D=master&merge_request%5Btarget_project_id%5D=7656#3a526d0ca8449c5d3b0245f4db072da87d6b1514_0_52

I also wasn't sure if this admin-type work even belongs here. If not, we can put it in some other Interop project, like maybe the dev-portal-team project.