Add API-based EntityLookupTrait

[colemanw]

Overview

Adds a helper class to make it easy to lookup entity values.

Technical Details

This trait can be mixed into any php class (e.g. a quickform or a smarty page or anything really) and removes the busywork of figuring out how to efficiently load, store and retrieve entity values.

To Use:

First you define() an entity by giving it a nickname and setting the id (or other unique identifiers):

$this->define('Contact', 'the_user', ['id' => $cid]);

Then you can lookup() any values you want. Behind the scenes, values will be lazy loaded as you need them and cached in memory to prevent repeated queries.

$yourName = $this->lookup('the_user', 'display_name');

[civibot]

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[eileenmcnaughton]

This looks pretty cool - I don't know if it fully meets all the form needs but I'll merge it & tinker around with it & see if there are any gaps that need a bit more