Add APIv4 and pseudoconstants for RelationshipCache

[colemanw]

Overview

Followup on the new RelationshipCache entity to add more metadata and an api + unit test.

[civibot]

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[eileenmcnaughton]

test this please

[eileenmcnaughton]

@colemanw related fail

api\v4\Entity\RelationshipTest::testRelCache
API_Exception: Invalid field 'near_contact_id'

/home/jenkins/bknix-dfl/build/core-17879-579vu/web/sites/all/modules/civicrm/Civi/Api4/Query/Api4SelectQuery.php:474
/home/jenkins/bknix-dfl/build/core-17879-579vu/web/sites/all/modules/civicrm/Civi/Api4/Query/Api4SelectQuery.php:356
/home/jenkins/bknix-dfl/build/core-17879-579vu/web/sites/all/modules/civicrm/Civi/Api4/Query/Api4SelectQuery.php:334
/home/jenkins/bknix-dfl/build/core-17879-579vu/web/sites/all/modules/civicrm/Civi/Api4/Query/Api4SelectQuery.php:321
/home/jenkins/bknix-dfl/build/core-17879-579vu/web/sites/all/modules/civicrm/Civi/Api4/Query/Api4SelectQuery.php:230
/home/jenkins/bknix-dfl/build/core-17879-579vu/web/sites/all/modules/civicrm/Civi/Api4/Query/Api4SelectQuery.php:114
/home/jenkins/bknix-dfl/build/core-17879-579vu/web/sites/all/modules/civicrm/Civi/Api4/Query/Api4SelectQuery.php:129
/home/jenkins/bknix-dfl/build/core-17879-579vu/web/sites/all/modules/civicrm/Civi/Api4/Generic/DAOGetAction.php:86
/home/jenkins/bknix-dfl/build/core-17879-579vu/web/sites/all/modules/civicrm/Civi/Api4/Generic/DAOGetAction.php:74
/home/jenkins/bknix-dfl/build/core-17879-579vu/web/sites/all/modules/civicrm/Civi/Api4/Provider/ActionObjectProvider.php:68
/home/jenkins/bknix-dfl/build/core-17879-579vu/web/sites/all/modules/civicrm/Civi/API/Kernel.php:150
/home/jenkins/bknix-dfl/build/core-17879-579vu/web/sites/all/modules/civicrm/Civi/Api4/Generic/AbstractAction.php:238
/home/jenkins/bknix-dfl/build/core-17879-579vu/web/sites/all/modules/civicrm/tests/phpunit/api/v4/Entity/RelationshipTest.php:46
/home/jenkins/bknix-dfl/extern/phpunit7/phpunit7.phar:615

[colemanw]

@eileenmcnaughton @totten this is failing because #17734 didn't get merged :(
Therefore the test db is still '5.27.alpha1', therefore none of the new fields in civicrm_relationship_cache are visible to the api.

I could "fix" it in this PR by updating the test db to 5.29, but this is going to keep happening, and it's going to frustrate people when they can't figure out why tests seem to be failing for no reason.

[eileenmcnaughton]

test this please

[eileenmcnaughton]

I think an alternative got merged so hopefully this can pass now