[DPE-2994] No more relational databag usage

[juditnovak]

Overview

This PR is addressing issue #163

Rationale

The Relational Databag is not to be addressed directly but only via interface functions.
Part of the relational data is now "hiding" in Juju Secrets and are not exposed on the databag anymore.
The data_platform_libs/data_interfaces DatabaseRequires and DatabaseProvies interfaces ensure transparent and safe access to all relational data. Outside of these functions, no access/manipulation of this data can be guaranteed in the future.

Module Changes

Relational Databag usage is replaced with DatabaseRequires interface calls.

[weiiwang01]

/canonical/self-hosted-runners/run-workflows e2a1c83

[github-actions]

Test coverage for e2a1c83

Name                Stmts   Miss Branch BrPart  Cover   Missing
---------------------------------------------------------------
src/charm.py          533     41    172     31    89%   184-187, 379-380, 580, 611, 617, 662, 697-698, 749-756, 761, 863->868, 867, 869, 874-875, 935, 953, 960, 1050, 1059, 1071, 1092, 1101, 1120, 1124, 1153, 1206, 1338, 1360, 1367->1369, 1412->exit, 1424, 1440, 1477, 1486-1487
src/cos.py             15      0      0      0   100%
src/exceptions.py      17      1      2      1    89%   41
src/types_.py          16      0      0      0   100%
---------------------------------------------------------------
TOTAL                 581     42    174     32    90%

Static code analysis report

Run started:2023-11-14 14:15:17.157053

Test results:
  No issues identified.

Code scanned:
  Total lines of code: 4314
  Total lines skipped (#nosec): 1
  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):

[yanksyoon]

LGTM, thanks!

[juditnovak]

The PR was merged on the base repository directly