Introduce HookEssentials

[Al2Klimov]

Introduce Icinga\Application\Hook\HookEssentials as the shared API for hook base classes to register and retrieve hook implementations through their own type.

This moves existing core hook classes to methods such as register(), all(), first(), and isRegistered(), while keeping the underlying hook registry behavior unchanged.

The new trait centralizes common hook behavior and lets hook base classes define their registry name once through getHookName(). It also adds getModule() for hook implementations that belong to a module namespace.

Existing direct uses of Hook::has(), Hook::all(), Hook::first(), and Hook::register() are replaced where a typed hook base class is available. The old low-level APIs and Module::provideHook() are marked as deprecated in favor of Hook\HookEssentials.

[Al2Klimov]

Test

1. Install Fedora 42
2. Apply https://github.com/Al2Klimov/ansible-icinga-fedora
3. Downgrade to https://git.icinga.com/packages/icingaweb/-/jobs/817857
4. Ensure /icingaweb2/health shows Icinga DB and Redis
5. In /usr/share/icingaweb2/modules/icingadb/run.php, comment out $this->provideHook('health', 'RedisHealth');
6. Ensure /icingaweb2/health shows Icinga DB only
7. In /usr/share/icingaweb2/modules/icingadb/run.php, add \Icinga\Module\Icingadb\ProvidedHook\RedisHealth::register();
8. Ensure /icingaweb2/health shows Icinga DB and Redis again = it works

[Al2Klimov]

@lippserd Please have a quick look here. This PR would allow to make

• LoginButtonHook: additional buttons below the login form #5442
• Implement password policy with hook #5419
• Request hook #5433
• Provide less vars loader hook #4774
• Allow custom csp header #5477
• and Allow editing of the CSP trusted image sources. #5337

gleich gescheit.

[sukhwinder33445]

Please rebase.

[lippserd]

I made the following changes:

• Renamed Essentials to HookEssentials throughout
• Replaced the trait-alias pattern in LoginButtonHook and RequestHook (use Essentials { register as protected parentRegister; } + register() override) with an isAlwaysRun(): bool class method override; register() now accepts ?bool $alwaysRun = null and falls back to static::isAlwaysRun()
• Added getModule(): ?Module, ported from Icinga DB Web's HookUtils, generalized to return null for hooks outside a module namespace
• Completed two missed migrations: Hook::first('Pdfexport') in Pdf.php and Hook::first('ThemeLoader') in StyleSheet.php

@Al2Klimov please have a look since I have amended some of the changes into your commits.
@TheSyscall please review.

[TheSyscall]

• I searched through the codebase and I can't find any hook that doesn't use the new HookEssentials methods. (At least in icingaweb itself)
• Tested the functionality behind these hooks, and they seem to work just fine.
• getModule should probably be final, but that is sadly not possible in PHP.

Finding(s):

getHookName inside the hook implementations should be made final in all instances, overriding it could lead to strange bugs. But that would be entirely self-inflicted.

[TheSyscall]

LGTM 👍