[REF] Add caching to function to determine if activity type is permitted.

[eileenmcnaughton]

Overview

This reduces the number of queries that run when calling Activity.get api

Before

Currently the Activity.get api gets a number of queries and then checks the permission for each one (this is something I'd like to change) and in each check it runs an sql query to determine if the contact can access the activity type of that activity. There are other places (forms, pages) where permissions are determined on multiple activities by running multiple queries

After

A list of accessible activity types is cached in a php static variable. The query only runs once

Technical Details

This is being cached in a php static variable rather than being queried multiple times.

It would be nice if this could be cached in Redis in a future iteration

We would want to be able to flush this whenever one of the following
happens

 1) an activity type is created, updated, deleted
 2) a component is enabled or disabled
 3) a CMS permission change takes place

It seems like it would be good for functions that do caching to register themselves
against actions that may affect them.

Comments

[civibot]

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[colemanw]

The function getPermittedActivityTypes looks like it would be amenable to a test :)

[eileenmcnaughton]

@colemanw it's pretty well covered by api tests which were added in conjunction with an earlier step in the refactoring