Flag silently ignored when contains invalid characters

[austinpray-mixpanel]

Describe the bug

Flags Must consist only of alphanumeric characters, '_', '-', or '.' and not exceed 45 characters

If my CI suite accidentally contains a slash or some other character, the flag is silently dropped.

To Reproduce
Steps to reproduce the behavior:

1. Use uploader v0.2.4
2. send a flag as -F ci/js-unit-tests
3. The upload succeeds but the flag is blank

Expected behavior

I would expect it to bail out with "Invalid flag: flags Must consist only of alphanumeric characters, '_', '-', or '.' and not exceed 45 characters"

Additional context

If you think this is too much of a BC break, I could accept this being hidden behind a flag like CODECOV_STRICT_FLAGS=1 or something.

[drazisil-codecov]

@austinpray-mixpanel, To confirm, you are saying it's blank in the POST URL or on the site?

[austinpray-mixpanel]

It's blank on the post URL and on the side

[2022-07-21T04:46:38.293Z] ['info'] 
     _____          _
    / ____|        | |
   | |     ___   __| | ___  ___ _____   __
   | |    / _ \ / _` |/ _ \/ __/ _ \ \ / /
   | |___| (_) | (_| |  __/ (_| (_) \ V /
    \_____\___/ \__,_|\___|\___\___/ \_/

  Codecov report uploader 0.2.4
[2022-07-21T04:46:38.302Z] ['info'] => Project root located at: <snip>
[2022-07-21T04:46:38.303Z] ['info'] ->  Token found by arguments
[2022-07-21T04:46:38.678Z] ['info'] Searching for coverage files...
[2022-07-21T04:46:38.831Z] ['info'] => Found 1 possible coverage files:
  ./coverage.xml
[2022-07-21T04:46:38.831Z] ['info'] Processing ./coverage.xml...
[2022-07-21T04:46:38.943Z] ['info'] Detected Jenkins CI as the CI provider.
[2022-07-21T04:46:38.947Z] ['info'] Pinging Codecov: https://codecov.io/upload/v4?package=uploader-0.2.4&token=*******&branch=austin-cc-python&build=78766&build_url=<snip>&commit=5e74263d39e6864962adf37fe7faaf2d0fa7fba7&job=&pr=42851&service=jenkins&slug=<snip>&name=&tag=&flags=&parent=
[2022-07-21T04:46:39.225Z] ['info'] https://codecov.io/<snip>
<snip>
[2022-07-21T04:46:39.225Z] ['info'] Uploading...
[2022-07-21T04:46:39.413Z] ['info'] {"status":"success","resultURL":"<snip>"}

You can see flags=

_{<snip> is redacted}