[Slack][Membership] Skip MembershipOptionsModal for users who have only one capability

[chungl]

Many equipment trainers are regular members with no special privileges besides equipment authorization. When they use the /membership command, they are greeted with a modal that asks "What do you want to do?" that has an empty select field. When they click on it, they see that they have one capability from which to choose.

This is suboptimal UX and unnecessary friction.

When we handle MembershipOptionsModal, we should check the options length before we post the view. It may be as simple as delegating the return value to the handle method of the modal associated with the only option. There may be some complexity there; I haven't explored that yet.

[Jnesselr]

It won't be delegated to the handle of the returned option, since that's what happens when you submit that option and at that point, we're at "what do we display". That's handled in this controller which really should be moved but I'll get to that later. It creates a new MembershipOptionsModal and then uses the trigger id of the request to open it. We can call getOptions on that modal and it'll get the valid options for the current user. If there's one return value, we can call that.

There are some caveats to this, though. I did have "Cancel my membership" enabled and then disabled it when we added the "cancellation reason" field request. We can remove that entirely, but just thinking through the logic if that was the only option available, we'd cancel their membership. We could and should have the basic UI/UX idea of "nothing changes without confirmation" (and wouldn't you know it, past me made CancelMembershipConfirmationModal). If we did have that still enabled as an option, a member would run that, see "Are you sure you want to cancel your membership" and conclude "I can only cancel my membership using this".

Here's what I think some good options are:

1. Have it pre-selected as the option you're going to go with so you just hit "submit". The benefit to this that I like is if you ever get a second item on that list, you won't be surprised to see the page AND you'll get the visual feedback of "I need to select something"
2. Add a training command directly. /train or something. Empty arguments brings up that form. If you at tag people in slack and give the names of equipment, maybe we can do some rough matching and auto fill those? Just a thought.

For just checking it off the list, I think the first option is best and it would benefit greatly from #42 .

[Jnesselr]

I think the fixes in #150 are sufficient to consider this issue closed. The minor amount of friction is fine in the event that the user gets more options, since all they have to do is hit Submit.

I thought about making it go directly to the equipment authorization page, and I'd need to update SlackMembershipCommandController to get the list of membership options for the customer, verify that there was only one, and that that option was the trainable equipment one. The constructor of the membership options modal would then have to run through the options again or accept them as parameters which felt weird code wise.

If you disagree with my reasoning on it, we can talk through pros/cons. I definitely see where you're coming from though on making it as easy as possible for members who are only trainers and nothing else to access the equipment authorization page. I could probably be convinced to change the behavior if the code doesn't feel icky. In fact I'm so "against" this that I made a PR for it #151 and will merge it if you don't think that's too icky code wise. 😅 (wow this comment was a roller coaster)

[Jnesselr]

Ran some numbers on current membership. 59 people can only train on one item, now auto selected for them. There are 65 people who who can only train on equipment and would jump straight to the equipment training. The Venn diagram between the two is 36, meaning there are 36 people who would jump straight to the equipment training modal with the single user selected. 10% of our users having a good experience and needing to adjust their flow slightly if they take on more responsibility seems reasonable to me.