Devops: Add Codecov token to CI

[agoscinski]

After merge got this error

Error: Codecov: Failed to properly create commit: The process '/home/runner/work/_actions/codecov/codecov-action/v4/dist/codecov' failed with exit code 1

https://github.com/aiidateam/aiida-restapi/actions/runs/9188834086/job/25269509068

Not sure why this did not appear during PR. Hope this fixes it

EDIT: I see it did not fail because of

Tokenless uploading is unsupported. However, PRs made from forks to the upstream public repos will support tokenless (e.g. contributors to OS projects do not need the upstream repo's Codecov token). For details, see our docs

https://github.com/codecov/codecov-action?tab=readme-ov-file#breaking-changes I will create nonupstream branch to test

EDIT2: Okay with this PR https://github.com/aiidateam/aiida-restapi/pull/68 we can verify that the fix works. As it is a branch on the upstream repository it fails when the token is commented out (see second commit that fails while first commit works)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 93.39%. Comparing base (3f14ea2) to head (a6744e9). Report is 8 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #67 +/- ## ======================================= Coverage 93.39% 93.39% ======================================= Files 28 28 Lines 999 999 ======================================= Hits 933 933 Misses 66 66 ``` | [Flag](https://app.codecov.io/gh/aiidateam/aiida-restapi/pull/67/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=aiidateam) | Coverage Δ | | |---|---|---| | [pytests](https://app.codecov.io/gh/aiidateam/aiida-restapi/pull/67/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=aiidateam) | `93.39% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=aiidateam#carryforward-flags-in-the-pull-request-comment) to find out more.

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[superstar54]

Hi @agoscinski , thanks for the PR!

Since @unkcpz mentioned wanting to take responsibility for the aiida-restapi in the aiida meeting, I added him as the reviewer here. For the future PR, you can also add him as the reviewer.