Add SMTP configuration

[amandahla]

Overview

Synapse can send e-mail notifications to users regarding new messages, events, etc. To make it possible, an SMTP server must be configured.

Also, this PR addresses the following issues commented on #43:

• Convert CharmState to dataclass
• Change from_charm to use CharmBase as parameter
• Pass Datasource and SAMLConfiguration as parameters
• Sort config.yaml file alphabetically
• Make database and saml variables privates
• Change functions order in workload.py accordingly to its usage

Plus:

• Add use-existing parameter to integration test so is easier to run integration tests locally without waiting for deploy every time.
• Add cos mark so it can be skipped.

Rationale

Send e-mail notifications.

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

[github-actions]

Test coverage for 49cf7ad

Name                            Stmts   Miss Branch BrPart  Cover   Missing
---------------------------------------------------------------------------
src/actions/__init__.py             3      0      0      0   100%
src/actions/register_user.py       21      0      2      0   100%
src/actions/reset_instance.py      21      3      2      1    83%   54-58
src/charm.py                      107      4     14      1    96%   112-113, 165-166
src/charm_state.py                 52      1     12      1    97%   121
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                    103      2     26      4    95%   68, 80->exit, 116, 181->186
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      5     20      2    96%   144, 315, 399-401
src/synapse/workload.py           187      6     26      6    94%   343-344, 360, 390->393, 409->412, 458, 460, 465
src/user.py                        24      0      4      0   100%
---------------------------------------------------------------------------
TOTAL                             933     36    134     20    95%

Static code analysis report

Run started:2023-10-04 13:27:57.379690

Test results:
  No issues identified.

Code scanned:
  Total lines of code: 4527
  Total lines skipped (#nosec): 7
  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):