Allow to define rename fields in $filterFields

[Lakshan-Madushanka]

Currently, if we need to restrict fields and rename fields, we have to define both $availableFields and $renamedFields. It causes code duplication. We can avoid it with this feature.

[abbasudo]

Hey @Lakshan-Madushanka.

Please inform me of your solution before applying it so we can discuss it. And remember in Purity simplicity and extendibility is a priority.

[abbasudo]

Currently, FilterFields values act as restrictions for filters

$filterFields = [
  'title' => ['$eq'],  // title will be limited to the eq operator
  'title' => '$eq',    // works only for one restricted operator
  'title:$eq',         // same as above
  'title',             // this won't be restricted to any operator
];

which itself is $restrictedFilters responsibility. However, we decided to merge it with $filterFields as it's more convenient and easier to implement and prevents duplication.
The restriction feature is more important and is used more often than renaming fields. If you have any implementation of defining renamed columns in $filterFields it should not conflict with the current functionalities of that variable.

[Lakshan-Madushanka]

@abbasudo What we do about this ?. How about something like following,

$filterFields = [ 'title as post_title' => ['$eq'], // title will be limited to the eq operator ];

We don't need to break any existing functionality. We can check for 'as' keyword existence, if so we can consider right side string as renamed column.

[Lakshan-Madushanka]

@abbasudo How should we handle this?