[Feature] relation filter

[aknEvrnky]

Why this PR exists?

This pull request includes a new feature which is RelationFilter for database querying. It provides us filtering the pages according to their relations.

How to use it?

Usage is quite basic. Here an example:

$database = $client->databases()->find('< DB_ID >');

$query = Query::create()
    ->changeFilter(
        CompoundFilter::and(
            DateFilter::property('delivery_date')->onOrBefore(date('Y-m-d')),
            RelationFilter::property('Project')->contains('< PAGE_ID >'),
        )
    )
    ->addSort(Sort::property("delivery_date")->ascending())
    ->changePageSize(30);

$result = $client->databases()->query($database, $query);

[codecov-commenter]

Codecov Report

Merging #185 (b2b4c93) into main (5c2a4bd) will decrease coverage by 7.93%.
The diff coverage is 96.96%.

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@@             Coverage Diff              @@
##               main     #185      +/-   ##
============================================
- Coverage     99.12%   91.19%   -7.93%     
- Complexity     1198     1211      +13     
============================================
  Files           129      130       +1     
  Lines          3886     3919      +33     
============================================
- Hits           3852     3574     -278     
- Misses           34      345     +311     

Impacted Files	Coverage Δ
src/Databases/Query/RelationFilter.php	96.77% <96.77%> (ø)
src/Databases/Query/DateFilter.php	98.43% <100.00%> (+0.05%)	⬆️

... and 24 files with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[mariosimao]

Hi @aknEvrnky, thanks for contributing! 😄

Your changes are now available on v1.6.0.

[aknEvrnky]

Hi @aknEvrnky, thanks for contributing! 😄

Your changes are now available on v1.6.0.

Thanks, I'll be contributing if I see anything missing again.