Update codecov coverage config file

[CasperWA]

Properly set threshold.

This is implemented with reference to https://github.com/aiidateam/aiida-optimade/blob/develop/.codecov.yml, which seems to work for this PR. (Project coverage decrease of 0.16 % and it's still accepted, only the patch coverage is not accepted due to a difference of more than 0.5 % than from what is expected).

[ml-evs]

This is one of the many incantations I've tried to get this working in the past, so good luck...

[ml-evs]

I'd suggest adding a random function somewhere in the code that would break the coverage in a separate commit to test that this actually does anything.

[codecov]

Codecov Report

Merging #672 (99c0f97) into master (1160b88) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #672   +/-   ##
=======================================
  Coverage   93.30%   93.30%           
=======================================
  Files          61       61           
  Lines        3300     3300           
=======================================
  Hits         3079     3079           
  Misses        221      221           

Flag	Coverage Δ
project	93.30% <ø> (ø)
validator	66.06% <ø> (ø)

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[CasperWA]

e16222e adds enough non-covered lines to decrease the overall coverage of the code by 0.12 %. But it's still listed as a pass, since this is below 0.5 % 👍
The patch fails since it's expected to hit 93.30 %, but only hit 20.00 % (a difference of 73.30 %, much more than 0.5 %) so that's fair enough.

[CasperWA]

Note: The documentation on how to fill out the config file is here.

[CasperWA]

From this line it seems the fetch depth should be set differently as well.

[CasperWA]

I think will work out, so I'll remove the temporary commit (resulting in no code changes) and then it should all be fine.

Last question though. Since I renamed the "project" status to "project/optimade", should we rename the flag from project to optimade as well? Or maybe just keep it so that the history on codecov persists?

Also, as a summary, I have set all the thresholds to 1%, except for patch, which is set to 5%. Is this fine?

[ml-evs]

Thanks for this @CasperWA, definitely a better way of doing things. I'm happy with these thresholds, we can always tweak them again if need be.