add missing strip_prefix

[Thanhphan1147]

The code to strip the ingress prefix was present when synapse was using ingress v1 but was missed when moving to the v2 lib. So this PR adds it. synapse can't handle prefix so this is needed to function properly.

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)

[github-actions]

Test coverage for c919b54

Name                                    Stmts   Miss Branch BrPart  Cover   Missing
-----------------------------------------------------------------------------------
src/actions/__init__.py                     1      0      0      0   100%
src/actions/register_user.py               21      0      2      0   100%
src/admin_access_token.py                   9      0      0      0   100%
src/backup.py                             175      5     20      2    96%   353-354, 423-424, 481->483, 484
src/backup_observer.py                    134     16     12      0    89%   132-135, 140-143, 179-182, 211-214
src/charm.py                              303     20     70     11    92%   140->142, 145, 251, 255-256, 262-263, 284-285, 314, 321, 401-405, 408-409, 437-439, 459, 495-496
src/charm_types.py                         30      0      0      0   100%
src/database_client.py                     57      1      8      4    92%   35, 47->exit, 69->exit, 88->98
src/database_observer.py                   50      4      2      0    92%   61-64
src/exceptions.py                           3      0      0      0   100%
src/matrix_auth_observer.py                68      8     12      3    86%   63, 66, 145, 159-163
src/media_observer.py                      45      4      2      1    89%   60-62, 81
src/mjolnir.py                            102      3     30      3    95%   85, 94->110, 115-119
src/observability.py                       14      0      0      0   100%
src/pebble.py                             203     25     46     12    85%   57->62, 176->exit, 187-191, 225-226, 246-247, 300->305, 310-311, 323-324, 326-327, 360, 362, 364, 366, 368, 396, 448-453
src/redis_observer.py                      39      3      4      0    93%   63-66
src/s3_parameters.py                       22      0      4      0   100%
src/smtp_observer.py                       61      4     14      2    92%   82-86, 89, 108->113
src/state/__init__.py                       0      0      0      0   100%
src/state/charm_state.py                  128      9     32      7    90%   166, 170, 191, 216, 222, 228, 232-233, 316
src/state/mas.py                           18      4      2      1    75%   41-44, 57
src/state/validation.py                    32      0      2      0   100%
src/synapse/__init__.py                     4      0      0      0   100%
src/synapse/admin.py                       19      2      2      0    90%   40-41
src/synapse/api.py                        175      3     20      3    97%   176, 229, 402
src/synapse/workload.py                   138      6     24      0    94%   401-402, 412-415
src/synapse/workload_configuration.py     148     26     34     12    79%   88->exit, 92-93, 141-142, 171, 191-192, 224-225, 258, 267-268, 283, 288-289, 310-311, 330->335, 336, 354->356, 366-367, 395, 403->405, 405->407, 412-413, 433->440, 443, 463-464
src/user.py                                23      0      2      0   100%
-----------------------------------------------------------------------------------
TOTAL                                    2022    143    344     61    91%

Static code analysis report

Working... ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 100% 0:00:00
Run started:2024-12-09 15:44:53.721842

Test results:
  No issues identified.

Code scanned:
  Total lines of code: 10926
  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):