Add anonymize user action

[gtrkiller]

Overview

Add an action to deactivate/anonymize users.

Rationale

GDPR compliance

Juju Events Changes

N/A

Module Changes

N/A

Library Changes

N/A

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)

Screenshot before and after anonymization:

[yanksyoon]

Very cool! Minor comments!

[amandahla]

Is it possible to add a screenshot to the PR of how it will look after a user is anonymized?
"It can also mark the user as GDPR-erased. This means messages sent by the user will still be visible by anyone that was in the room when these messages were sent, but hidden from users joining the room afterwards."

[yanksyoon]

LGTM!

[github-actions]

Test coverage for 1086ead

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                      196      8     36      4    95%   125-126, 178-179, 198-199, 240, 254
src/charm_state.py                 64      1     12      1    97%   141
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                      77     10      6      3    84%   90-91, 93, 95, 109-114
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           200      6     30      5    95%   361-362, 378, 427->430, 476, 478, 483
src/user.py                        24      0      4      0   100%
---------------------------------------------------------------------------
TOTAL                            1023     41    158     20    95%

Static code analysis report

Run started:2023-11-03 12:47:49.174524

Test results:
  No issues identified.

Code scanned:
  Total lines of code: 5235
  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):

[amandahla]

LGTM

[arturo-seijas]

LGTM