Use entry points to support plugin mechanism.

[shanchenqi]

As we have discussed in Issue #496, we implemented grimoirelab-elk-gitee as a plugin. In order to support this plugin solution, we need to use entry points as I created in this pull request.

[coveralls]

Pull Request Test Coverage Report for Build 2615896479

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 40 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.02%) to 82.366%

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Files with Coverage Reduction	New Missed Lines	%
/home/runner/work/grimoirelab-elk/grimoirelab-elk/grimoire_elk/utils.py	40	68.89%
<!--	Total:	40		-->

Totals
Change from base Build 2555428948:	-0.02%
Covered Lines:	8842
Relevant Lines:	10735

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💛 - Coveralls

[shanchenqi]

Hi, @sduenas, Thank you for your code review. I have updated my pull request according to your advice.

[shanchenqi]

Excuse me, I force to push the commits again in order to squash the commits into one.

[shanchenqi]

LGTM but, would you mind to change the message of the commit? Follow the guidelines I mentioned before (you can also use part of the text included in the changelog entry). Thanks!

OK, I got it and updated the code. Thank you~

[sduenas]

@shanchenqi last thing, I realized the PR doesn't contain the latest changes of the repo history. Would you mind to rebase it with master before I merge it?

[shanchenqi]

@shanchenqi last thing, I realized the PR doesn't contain the latest changes of the repo history. Would you mind to rebase it with master before I merge it?

HI, @sduenas , I have rebased the commit messages and all checks passed. Thanks for your help and your affirmation.

[sduenas]

@shanchenqi thanks for the PR!

[shanchenqi]

@shanchenqi thanks for the PR!

It's my pleasure!