Bug 37389: ExtendedAttributes mixin

Bug 37389: ExtendedAttributes mixin

This is what we're doing here:

- Creating a new mixin called ExtendedAttributes.pm
- Moving the extended_attributes 'join' logic out of REST/Plugin/Query and instead applying it to the aforementioned Mixin. Moving this to this level allows for this consistent behavior to happen on all search queries including, but not limited to, search queries happening on the REST API.
- Applying this Mixin to Patrons and ILL::Requests (we don't apply it to AdditionalFields.pm here yet because no AdditionalFields supporting classes have the extended_attributes accessor yet, I'll tackle this when rebasing 35287)

- The aforementioned mixin does the following:
-- Generates dynamic accessors for extended_attributes e.g. if there is a borrower attribute with code 'height', the 'extended_attributes_height' accessor is generated dynamically if a search with 'prefetch'=>'extended_attributes' AND the extended_attribute.code = 'height' is performed.
-- Rewrites the 'join' entries in the query to have the aliases as above.
-- Rewrites the WHERE conditions to match the above ruleset.

Example:

A DBIX search query as follows:

[
        {
            '-and' => [
                [
                    {
                        'extended_attributes.attribute' => { 'like' => 'abc%' },
                        'extended_attributes.code'      => 'CODE_1'
                    }
                ],
                [
                    {
                        'extended_attributes.code'      => 'CODE_2',
                        'extended_attributes.attribute' => { 'like' => '123%' }
                    }
                ]
            ]
        }
    ]

Results in the following SQL:

    SELECT
      `me`.`borrowernumber`
    FROM
      `borrowers` `me`
      LEFT JOIN `borrower_attributes` `extended_attributes_CODE_1` ON (
        `extended_attributes_CODE_1`.`borrowernumber` = `me`.`borrowernumber`
        AND `extended_attributes_CODE_1`.`code` = ?
      )
      LEFT JOIN `borrower_attributes` `extended_attributes_CODE_2` ON (
        `extended_attributes_CODE_2`.`borrowernumber` = `me`.`borrowernumber`
        AND `extended_attributes_CODE_2`.`code` = ?
      )
    WHERE
      (
        (
          (
            `extended_attributes_CODE_1`.`attribute` LIKE ?
            AND `extended_attributes_CODE_1`.`code` = ?
          )
          AND (
            `extended_attributes_CODE_2`.`attribute` LIKE ?
            AND `extended_attributes_CODE_2`.`code` = ?
          )
        )
      )

What fixes the performance issue that originated this work is the 'AND `extended_attributes_CODE_1`.`code` = ?' that was missing on the LEFT JOIN.

All of the above is explained using Borrowers and Borrower attributes, but it all also applies to ILL::Requests and ILL::Request::Attributes.

Co-authored-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>