Add action to promote a user to an admin

[amandahla]

Overview

To promote a user to an admin you need to interact with the Synapse API. This action makes this easier so the user can use a juju command to do that like:

juju run-action synapse/0 promote-user-admin username=user1 --wait

Note:

• The API call to do that requires an admin access token.
• Mjolnir has the same requirement so the interaction with Synapse and peer data to get this admin access token is already implemented there.
• This PR moves this implementation to a new module called Secret Storage so both, Mjolnir and the new action, can get an admin access token that is stored on peer data.
• Mind that is a little bit different from the way it was implemented on Flask because to get an admin access token, we need Synapse to be running, register a new user and then we'll have the token we need. Since this is not needed for the charm itself, it will only happen if Mjolnir is enabled or if the user runs the action to make a user an admin. That's why we are not observing the leader elected or relation joined event.
• Why not add the admin access token to charm_state? This would create a cyclic import like this: Cyclic import (actions -> actions.register_user -> synapse -> synapse.api -> charm_state -> secret_storage)

Plus:

• Create a Secret Storage module
• Change all references to admin_access_token to typing.Optional[str]
• Fix typo in src/charm_state.py

Rationale

Provide an easy way to make a user an admin.

Juju Events Changes

Module Changes

Library Changes

Checklist

• The charm style guide was applied
• The contributing guide was applied
• The changes are compliant with ISD054 - Manging Charm Complexity
• The documentation is generated using src-docs
• The documentation for charmhub is updated.
• The PR is tagged with appropriate label (urgent, trivial, complex)

[jdkandersson]

Have not looked at the tests yet

[gregory-schiano]

LGTM

[github-actions]

Test coverage for 6d99b5c

Name                            Stmts   Miss Branch BrPart  Cover   Missing
---------------------------------------------------------------------------
src/actions/__init__.py             3      0      0      0   100%
src/actions/register_user.py       22      0      2      0   100%
src/actions/reset_instance.py      21      0      2      0   100%
src/charm.py                      175      8     32      4    94%   124-125, 177-178, 197-198, 239, 253
src/charm_state.py                 63      1     12      1    97%   138
src/charm_types.py                 11      0      0      0   100%
src/database_client.py             53      1     10      3    94%   35, 47->exit, 69->exit
src/database_observer.py           54      4      6      0    93%   70-72, 88
src/exceptions.py                   4      0      0      0   100%
src/mjolnir.py                     76      8     20      2    88%   60-64, 73, 93-96
src/observability.py                9      0      0      0   100%
src/pebble.py                      75      9      4      2    86%   90-91, 93, 107-112
src/saml_observer.py               45      1      8      0    98%   64
src/synapse/__init__.py             3      0      0      0   100%
src/synapse/api.py                161      2     22      2    98%   207, 376
src/synapse/workload.py           192      6     30      5    95%   343-344, 360, 409->412, 458, 460, 465
src/user.py                        24      0      4      0   100%
---------------------------------------------------------------------------
TOTAL                             991     40    152     19    95%

Static code analysis report

Run started:2023-10-23 14:20:20.848145

Test results:
  No issues identified.

Code scanned:
  Total lines of code: 4996
  Total lines skipped (#nosec): 4
  Total potential issues skipped due to specifically being disabled (e.g., #nosec BXXX): 0

Run metrics:
  Total issues (by severity):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
  Total issues (by confidence):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
Files skipped (0):