Fix/issue 233 (staudenmeir#256)

* Add failing test

* reduce fatal error to phpstan failure

* WIP

* wip

* wip

* Refactoring

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Co-authored-by: Jonas Staudenmeir <[email protected]>

PHPStan level 2 (staudenmeir#253)

* phpstan-level-2

* Remove obsolete exclusion

* Add type hint

* Add PHPStan extension for Mockery

* Fix "method.notFound" errors

* Remove obsolete ignored error

* Resolve error

* PHPStan level 2 resolve identifier: property.notFound tests

* Fix incorrect TRelatedModel

* Refactoring

* Resolve remaining phpstan errors

* Fix namespace

* Formatting

* Refactoring

* Resolve error

* Resolve error

* Resolve error

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Co-authored-by: Jonas Staudenmeir <[email protected]>

Add additional methods (staudenmeir#232)

Refactoring

Support Laravel 11

Support Firebird

Merge branch '1.12'

Add RootAncestorOrSelf relation

Merge branch '1.12'

# Conflicts:
#	README.md
#	src/Eloquent/Relations/Graph/Ancestors.php
#	src/Eloquent/Relations/Graph/Descendants.php
#	tests/Graph/Models/Node.php

Make graph relationships concatenable