Fix how exc.response is checked while sending POST request to API

[amandahla]

Overview

While refreshing the charm with Mjolnir enabled, the charm will try to register the Mjolnir user again. This was throwing a RegisterUserError instead of checking that the API was returning that the User ID was already taken and then proceeding with getting the access token.

Rationale

Fix how the response is checked in cases where the user already exists so the Mjolnir configuration can proceed.

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)

[arturo-seijas]

LGTM

[amandahla]

This PR will fix #80

[gregory-schiano]

LGTM

[github-actions]

Test coverage for 43be3a5

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:2023-10-25 08:30:25.824231

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):