feat(svc): rename git_url to template_git_url and return git_url on all endpoints

[Panaetius]

closes #3564

[coveralls]

Pull Request Test Coverage Report for Build 6850695882

• 109 of 137 (79.56%) changed or added relevant lines in 12 files are covered.
• 8 unchanged lines in 7 files lost coverage.
• Overall coverage increased (+3.2%) to 86.024%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
renku/ui/service/serializers/templates.py	30	32	93.75%
renku/ui/service/views/v1/templates.py	19	23	82.61%
renku/ui/service/serializers/v1/templates.py	29	51	56.86%

Files with Coverage Reduction	New Missed Lines	%
renku/core/dataset/dataset.py	1	85.19%
renku/core/dataset/providers/dataverse.py	1	88.86%
renku/core/migration/m_0003__1_jsonld.py	1	87.68%
renku/core/migration/models/v3.py	1	97.24%
renku/ui/cli/init.py	1	96.9%
renku/ui/cli/service.py	1	28.57%
renku/command/rollback.py	2	78.7%

Totals
Change from base Build 6823291196:	3.2%
Covered Lines:	26522
Relevant Lines:	30831

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💛 - Coveralls

[Panaetius]

This should be ready. Feel free to merge. Need to coordinate with UI when it is merged