Add MessageTemplate api to v4

[eileenmcnaughton]

Overview

Basic add of MessageTemplate entity to apiv4 & use if from core form

Before

Not there

After

Ta-da

Technical Details

I'm looking to cleanup this form to use the apiv4 (I'd rather got the extra step & switch it to an afform but
that seems like too big a leap).

This switches the loading to use apiv4. Note that

1. I decided that it doesn't make sense to setCheckPermissions = FALSE - I think the form should not
   be availble to non-permissioned users (& perhaps a hook might like to play a role here).

2. I removed the inheritence from the parent which seemed to do 3 things

• added admin.css - none of the classes seemed to apply
• added iconpicker - didn't seem to apply
• loaded the defaults - which this change does on the form more succinctly

Comments

[civibot]

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[seamuslee001]

@eileenmcnaughton i think that needs to be a subdirectory up i.e. in Civi/Api4

[eileenmcnaughton]

opps you are right!

[colemanw]

RIP $Id$ we miss you.

[eileenmcnaughton]

test this please

[eileenmcnaughton]

@colemanw can you recheck this - I altered the form to use apiv4 as well & added some notes to the PR template & I'd like your feedback as apiv4 calls in core are fairly new

In the process of this I would note that I could also have used apiv3 & I can now see that the EntityFormTrait would have worked too (FYI ) but I was kind of trying to get familiar with increasing v4 usage in core

@mattwire we should possibly switch the EntityFormTrait to use apiv4. I think we could just switch

    $metadata = civicrm_api3($this->getDefaultEntity(), 'getfields', ['action' => 'create']);

to

    $metadata = civicrm_api4($this->getDefaultEntity(), 'getfields', ['action' => 'create']);

But we'd need some noisy fallback to apiv3 where there isn't a v4 entity

[colemanw]

Yes it all still looks good.