Add configuration entity for rules

@arijit acharya I appreciate your enthusiasm on this but this issue is at least partially blocked by needing a UX Design.

Okay @swirt, understood. I'm unassigning myself from this task for now. I'll keep an eye on the UX design progress and will be happy to assist once the blocker is resolved.

I've re-thought this a bit. Rather than using a custom config entity which would need entity references and a lot of extra overhead, this should just be a custom field (using the field API) to create a field that is made of of subfields. The field instance on the form will have unlimited cardinality. That solves the editorial experience nightmare that we would have with a config entity through entity references.

Here is a great video on the process making of custom fields

@tsquared212 I think this is ready to work on. I modified the field data in the description to match the UK design.

@tsquared212 I am wondering if the fork you pushed is missing some files. I am seeing a reference to
'AltTextRuleItemInterface' but do not see this interface in the code you pushed. I would also expect there would be a modification to AltTextValidationSettingsForm/php to add the field widget.

Also I am hoping this 2016 response is no longer true. If not I will be sad
https://drupal.stackexchange.com/questions/194661/config-entity-form-fie...

I think I have a solution to the cardinality problem. but I won't know it is a problem for sure until we get this field fully formed.

With the help of @dmundra I found a module that actually does what we need to do for adding and removing rules.
https://www.drupal.org/project/simplesamlphp_custom_attributes →
The second screen cap is from the module settings field.

swirt → credited dmundra → .

And here is an ajax example for add/remove

swirt → closed merge request !30

swirt → reopened merge request !30