[frontend] broken redirect to `/submissions`

[alxndrsn]

Repro

1. open https://staging.getodk.cloud/projects/203/forms/trees_update/
2. observe "Page Not Found" Error:

Additionally

The page header indicates that the user is "Not logged in", even when they are. Filed at #1698.

Cause

https://staging.getodk.cloud/projects/203/forms/trees_update/ seems to append /submissions to the URL. This works OK if the original URL had no trailing slash.

[matthew-white]

For some reason, I thought nginx removed the trailing slash. 🤔 Maybe it used to, or maybe I'm misremembering.

This does sound like a problem. I can think of a few different approaches:

1. Have nginx remove any trailing slash.
2. Have Frontend remove any trailing slash in the Vue router.
3. Change the logic that appends /submissions (code here) such that it's aware of the possibility of a trailing slash.

I think option (1) or (2) would be preferable. I think it'd simplify the Frontend code to be able to assume that there's no trailing slash.

[matthew-white]

I'm noticing that the description of #1263 also contemplates doing something general about trailing slashes, which makes sense to me in the context of that issue. I do feel like something general is the right approach, as opposed to option (3) above. Even option (2) would only change Frontend and wouldn't handle trailing slashes for Backend paths. @alxndrsn, what do you think? What if we handled it in the nginx layer?

One option is that we repurpose this issue to be about removing trailing slashes in general. Or we could file a separate issue about it.

[alxndrsn]

One option is that we repurpose this issue to be about removing trailing slashes in general. Or we could file a separate issue about it.

I think this issue is specific, and useful as-is. Maybe if a wider Issue is created, this can be added as a sub-issue of, or related to that one.

[alxndrsn]

Even option (2) would only change Frontend and wouldn't handle trailing slashes for Backend paths.

I don't necessarily see a problem with considering frontend & backend behaviour separately.