fix(authorization): canCreate should not return void

[AbdulRahmanAlHamali]

Retrofit methods cannot have a void return type. We either need to provide a return type, or a callback. This fixes the following exception:

java.lang.IllegalArgumentException: FiatService.canCreate: Must have either a return type or Callback as last argument.

I also added canCreate to the path, because it makes more sense.

[ajordens]

Argument /:userId/:resourceType/create makes sense to me.

[cfieber]

I was wrong about not changing the URI - this is breaking since we always do always call fiat on CREATE (and the enable/disable flag is on the fiat side).

We should leave the URI as is, or if we want to migrate it to the new form we should maintain a request mapping in fiat for the old form for some period of time - otherwise we are stuck in the situation of breaking front50 until we deploy new fiat (and then breaking old front50 until we deploy new).

[AbdulRahmanAlHamali]

The thing is, it is already broken in its current state, so if we sneak that change in, we won't break something that works

[cfieber]

Ah you are right - good point. Gonna

[cfieber]

@spinnakerbot cherry-pick 1.17

[spinnakerbot]

Cherry pick successful: #504