Add: Use external toml file for plugin configuration

[ghost]

What

Use an external toml file to store plugin configurations.
Rewrite http_links_in_tags plugin to use external config for exclusions as a demonstration of how other plugins can use it.

The location of the file is specified by the --plugins-config-file command-line argument added to the parser.
This argument has a default value of 'troubadix_config.toml'. This is the same as the config file in the vt repo.
This makes this release compatible with all old workflows and aliases that use Troubadix, as long as the new config file is present.
Otherwise, a different file must be specified, as Troubadix will no longer be able to run without a valid config file.
If no plugin is being run that uses external configuration, an empty but existing file is sufficient to be valid.
This is done to make it less likely that Troubadix will run without a configuration when it should have one.

This file must have an entry with the same name as the plugins Plugin.name attribute for each plugin that is executed during the Troubadix run that uses the new system.

[Plugin.name]
exclusions = ["foo", "bar"]

Plugins that are not executed or that do not use the new system do not need an entry in the toml file.

The values of the plugin entries can be any valid Toml structure that can be parsed into Python types.
This should allow the configuration of most plugins.
For example, http_tags_in_link just wants a list of exclusions. Which maps 1 to 1 from toml to python.

Plugins must use a class attribute to indicate if they depend on an external configuration. If nothing is set, as in existing plugins, the default of False is used. And then none of the new changes will apply to this plugin. Its function remains the same.

Plugins that use external config are passed the entire config, and are responsible for validating and extracting only the parts they want. They can then access the config via an instance attribute `config

Why

The purpose is to unify the configuration for all Troubadix plugins that are use case dependent / come from outside Troubadix.

Exclusion changes that are necessary for VT development, but do not change the Troubadix plugins, can then be part of the same PR that introduces the VT, and not require an additional Troubadix PR anymore.

Changes for VT Development

Rollout Step1

A toml file must be placed in the VT repository that contains all configuration for plugins that use the new file.

Rollout Step2

If a config file from a location other than the default location is to be used for QA, the troubadix invocation must be changed to reflect this.

Changes to config during normal VT development

Changes to the configuration of plugins that use the new system must be made in the vt repo toml file, not in Troubadix.
Changes to the config of plugins that have not yet been converted still need a Troubadix PR.

Converting existing plugins / Creating new Plugin with external config

Set class attribute requires_external_config = True
Override validate_plugin_config of the 'Plugin' base class.
Access config via self.config["key"].

References

VTOPS-115

Checklist

• Tests

[github-actions]

Conventional Commits Report

Type	Number
Changed	10
Added	1

🚀 Conventional commits found.

[codecov]

Codecov Report

Attention: Patch coverage is 71.73913% with 13 lines in your changes missing coverage. Please review.

Project coverage is 79.48%. Comparing base (318f02a) to head (81961da).
Report is 23 commits behind head on main.

Files with missing lines	Patch %	Lines
troubadix/troubadix.py	40.00%	6 Missing ⚠️
troubadix/plugin.py	78.94%	2 Missing and 2 partials ⚠️
troubadix/runner.py	66.66%	2 Missing ⚠️
troubadix/argparser.py	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #706      +/-   ##
==========================================
- Coverage   79.51%   79.48%   -0.04%     
==========================================
  Files          86       86              
  Lines        2910     2944      +34     
  Branches      611      616       +5     
==========================================
+ Hits         2314     2340      +26     
- Misses        450      457       +7     
- Partials      146      147       +1     

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