Investigate common repo for microservices

[joelvdavies]

We currently have inventory-management-system-api, object-storage-api, ldap-jwt-auth. We may potentially end up with another doing the relationships calculations. We various things in common for these such as authentication, common database setup etc. We also have migrations in ims-api that may in future need to extend to the others, and if we adopt the same error handling across the repos, that too. Having a common repo would avoid some of this duplication.