[enriched/github2] Add 'user_login' field

[zhquan]

This code adds the field user_login for all enriched items when the category is issue or pull_request.

Test updated accordingly.

Signed-off-by: Quan Zhou quan@bitergia.com

[coveralls]

Pull Request Test Coverage Report for Build 1185965170

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 24 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.02%) to 82.263%

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Files with Coverage Reduction	New Missed Lines	%
/home/runner/work/grimoirelab-elk/grimoirelab-elk/grimoire_elk/enriched/github.py	2	75.31%
/home/runner/work/grimoirelab-elk/grimoirelab-elk/grimoire_elk/enriched/github2.py	22	93.33%
<!--	Total:	24		-->

Totals
Change from base Build 1158427309:	-0.02%
Covered Lines:	8682
Relevant Lines:	10554

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💛 - Coveralls