Allow custom webservice to access / save management config

[Robert Lyon]

When we have a custom webservice that contains a function, eg module_lti_launch, that has the 'hasconfig' set to true we allow it to have the manage icon on the Admin -> Webservices -> External apps page.

This functionality was added with Bug 1892106

But we still need a way to display and save the config for that function when the service itself is not 'module/lti'

We need PluginAuthWebservice to be able to
1) add config fields for functions that belong to component 'webservice'
2) add config fields for functions that have their own plugin type, eg 'module/lti'

[Mahara Bot (dev-mahara)]

Patch for "master" branch: https://reviews.mahara.org/11296

[Mahara Bot (dev-mahara)]

Reviewed: https://reviews.mahara.org/11296
Committed: https://git.mahara.org/mahara/mahara/commit/407d0bc28eb9444867cf0745557b37863ae7dd40
Submitter: Cecilia Vela Gurovic (<email address hidden>)
Branch: master

commit 407d0bc28eb9444867cf0745557b37863ae7dd40
Author: Robert Lyon <email address hidden>
Date: Tue Sep 22 10:21:00 2020 +1200

Bug 1896547: Allow custom webservice function to populate config form

Change-Id: I12ee3bfb9ffd249dc66c8dbe621babecd6cb3145
Signed-off-by: Robert Lyon <email address hidden>