Create a new log endpoint for user reports that accepts dynamic strings

[steamclock-bot]

Automatically generated from steamclock/steamclog-swift#71

From a discussion in Slack:

User reports build up the report based on the text the user enters, but switching them to use the static string doesn’t work great, because it means all user reports will fold into the same error, which is not ideal for noticing or quick filing bugs.
Question is: do we just switch them to use static string anyway for now, and live with it being a bit more complicated to work with them. Or do we add some dynamic endpoint back into SteamcLog just for that (but that slightly defeats the purpose of trying to force people to use static strings and do it right, if there’s just an alternate endpoint that lets them do it wrong)?
The solution might be to have a dynamic non-fatal endpoint, but specifically name it “userReport” or something. That feels better then just going back to having some more generic “dynamicError” call, might be a little less likely to be accidentally misused. That function can eventually do a little bit of extra work. For example take a user info dictionary (with things like their device id for Spies), that it turns into tags on the sentry report, automatically collect a little more device info, attach the full text logs like we get with email reports, etc.