- After seeing frontend behaviour where the user could add the same
tag multiple times, and not get errors or be stopped doing so, we'll
change the backend to return a 409 if you tag a feature with a tag it
already has.
- Previous to this commit, the setup was to do `onConflict().ignore()`
which caused the frontend to not get any help from the backend as to
whether or not the operation was allowed
- This fix adds a custom error and adds a branch to the handleError util
method for handling just that error type with a 409.
- This caused a couple of tests to receive 409, probably due to
insufficient cleanup between tests. Adding faker as a dev-dependency and randomising
toggle names and tag values for each test reduces the chance that
we'll run into duplicate issues in the future for the tests that
touches this problem
fixes: #711
