Refactor: Switch to use username for document key instead of email

[mgroves]

Seems like username is a better choice for document key, especially since endpoints Follow, Unfollow, and Get profile all have username in their URL. Username is going to be used more for lookups than Email. Using a K-V operation in Couchbase is faster than a SQL query, if the result is only ever supposed to be ONE user/profile. So therefore, refactor to use K-V more often.

[mgroves]

Summary: The Conduit spec requires email for login, but otherwise username is used by most other endpoints. I'm making the assumption that login will happen less frequently than other operations, so therefore the overall app will be less affected by the overhead of SQL when using it for login and k/v elsewhere.

Endpoint analysis:

• Authentication - uses email, JWT token expires in 4 hours
• Registration - can use username for inserting new user
• Get Current User - as long as username is added to JWT token claims, can use username for lookup
• Update User - can use username
• Get profile - username is required
• Follow user - username is required
• Unfollow user - username is required
• List Articles - k/v was not really an option here in the first place
• Feed Articles - ditto
• Get Article - username is returned as part of author, not emai
• Create Article - username pulled from JWT token
• Update Article - username pulled from JWT token
• Delete Article - doesn't involve user
• Add Comments to an Article - username pulled from JWT token
• Get Comments from an Article - username is returned under 'author'
• Delete Comment - doesn't involve user
• Favorite Article - username part of author
• Unfavorite Article - username part of author
• Get Tags - user not involved

Handlers that needs changed:

• GetCurrentUserHandler - get username from claim instead of email, use GetUserByUsername instead of GetUserByEmail
• UpdateUserHandler - use GetUserByUsername instead of GetUserByEmail

Data access that needs changed:

• UserDataService::GetUserByEmail - should use SQL++ instead of key/value
• UserDataService::GetUserByUsername - should use key/value instead of SQL++
• UserDataService::RegisterNewUser - use username as key, not email
• User Model - Username should get [JsonIgnore], not Email
• UserDataService::UpdateUserFields - this can now update email, can no longer change username, use username as key instead of email
• UserDataService::GetProfileByUsername - use k/v instead of SQL++
• UserDataService::DoesExistUserByEmailAndUsername - switch around username/email address usage

Auth changes:

• AuthService::GenerateJwtToken Put username in the JWT claims (maybe in addition to email?)
• AuthService - will probably need a GetUsernameClaim

Migration changes:

• Rollback migration 2
• CreateIndexOnUsernameFieldInUsersCollection - since this is the latest migration, just rename and change it to index email instead of username
• Run all migrations up

Validator changes:

• No changes needed.

Controllers/Endpoints changes:

• No changes needed.

[mgroves]

I think this went pretty smoothly. All tests are passing, and a manual run-through of the endpoints is working okay.