back: link roles to users in User Service

[codegold79]

RoleIDs are not stored in the user table, nor is there a joint table that links user IDs and roleIDs. Consider these as well as other alternatives for linking users and roles.

[daved]

AC

• Create join table for users to have multiple roles
• Update relevant migration file(s)
• Ensure the user message contains the role ids
• (Daved) Investigate data structures for queries with joins
• (Daved) Investigate how limit/offset are affected by row data being duplicated in joins

*It's likely that we'll discuss whether to make multiple queries or a single query with fancy structure handling in order to hydrate a user and the related role data collection.

[daved]

Closed by #86