Tidy the bundle's structure and constraints

[loevgaard]

Fixes #30

Stacked on #52.

What is in

One source of truth for the tag bag check. Configuration::isTagBagBundleInstalled() and the four Assert calls in the extension both decided what counts as an installed tag bag bundle, with the package name and ^3.0 written twice. Both now call InstalledBundles::hasTagBagBundle(), and the constraint is a constant.

Symfony's exception types. The extension used Webmozart\Assert\Assert::true() and ::keyExists(), which throw \InvalidArgumentException. Symfony's convention for "bundle X requires bundle Y" is \LogicException, so that is what it throws now, with a message that also names the way out (client_side.enabled: false). The integration test asserting on the old type is updated.

Dependency constraints. symfony/event-dispatcher-contracts drops the ^2.5 branch: 2.x pairs with Symfony 5.4, which this bundle no longer supports, and Symfony 6.4's event dispatcher accepts ^3. Added a suggest section for nyholm/psr7, symfony/http-client, setono/tag-bag-bundle and setono/consent-bundle, which the README already told people to install.

What is deliberately out

AbstractBundle and PHP service configuration. The XML DI format is deprecated in Symfony 7.4 and removed in 8.0, so this migration is needed for Symfony 8 support, which is blocked on dependencies rather than on this bundle: setono/bot-detection-bundle allows ^5.4 || ^6.4 || ^7.0, and the consent and tag bag bundles have no Symfony 8 constraints either. Doing the migration now would be churn with no user-visible effect, so the extension keeps its comment marking the spot, and this stays with the Symfony 8 work.

Moving symfony/messenger to suggest. Server side tracking is on by default, so messenger is required for the default configuration. Making it optional would mean guarding the message and handler classes, which costs more than it saves.

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.93%. Comparing base (3cf8998) to head (7b3e810).

Files with missing lines	Patch %	Lines
src/DependencyInjection/InstalledBundles.php	75.00%	1 Missing ⚠️
...ncyInjection/SetonoMetaConversionsApiExtension.php	92.30%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master      #53      +/-   ##
============================================
- Coverage     82.08%   81.93%   -0.16%     
- Complexity      142      148       +6     
============================================
  Files            30       31       +1     
  Lines           480      487       +7     
============================================
+ Hits            394      399       +5     
- Misses           86       88       +2     

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