Coding style and broken links

[iRhonin]

Hi,
In this PR, I fixed two small things:

• Fix 2 blank line between function definitions in auth.py
• Fix broken links in CONTRIBUTING.md

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[iRhonin]

I signed it.

[googlebot]

CLAs look good, thanks!

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[hiranya911]

LGTM. Thanks for the contribution 👍