feat: Store user's metadata in database [FS-1828]

[atomrc]

FS-1828 [web] Store users in Database and only load unknown users

This will make sure that we download a user only once.

• at first start, all the users will be downloaded and stored into the database
• at subsequent loads, only the users that are listed (in connections or team members) that we do not have locally will be downloaded
• when a user is updated (via a websocket user.update message), we update the in-memory user and the database entry

This will:

• speedup webapp loading time (since all connections and team members won't be downloaded anymore)
• allow better offline support

[atomrc]

This is the major change here. Now getConnections and initTeam do not fetch user's metadata anymore (doing less side-effects).
Instead they return the userIds that needs to be loaded later on

The userRepository.loadUsers is responsible for loading the users from the DB and fetch the missing users on backend

[codecov]

Codecov Report

Merging #15002 (577622e) into dev (9a12711) will increase coverage by 0.16%.
The diff coverage is 50.71%.

@@            Coverage Diff             @@
##              dev   #15002      +/-   ##
==========================================
+ Coverage   43.12%   43.29%   +0.16%     
==========================================
  Files         641      642       +1     
  Lines       21545    21543       -2     
  Branches     4935     4932       -3     
==========================================
+ Hits         9292     9327      +35     
+ Misses      11066    11029      -37     
  Partials     1187     1187