Fixes, cleanup and tests

[mpsonntag]

This PR adds a couple of updates, fixes and tests

• reference IDs containing "https://doi.org/provided-id" are now allowed and parsed into the supported format "id: DOI:provided-id". To permit DOI references without prefix without updating the libgin function libgin.DataCite.AddReference the DataCite reference is updated before writing the DOI XML file in both web.startDOIRegistration and genxml. This code can be removed when an appropriately updated version of libgin is available.
• validation author ID checks to the external services ORCID and Publons were moved to their own function authorIDWarnings. This should make the external dependency clearer and also reduce testing times for the refactored tests.
• the checklist template has been updated to include repository size checks.
• the unused util functions ReferenceDescription, ReferenceSource and ReferenceID were removed.
• go template tests were refactored to reduce external dependencies: By locally serving datacite.yml files to test go template rendering instead of loading a datacite.yml file from the live gin server, the overall test times can be noticeably reduced and removes an external dependency.
• tests for the utils functions FormatCitation, URLexists and hasGitModules were added.

[coveralls]

Pull Request Test Coverage Report for Build 1963110626

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 32 of 50 (64.0%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.8%) to 48.306%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
cmd/gindoid/validation.go	13	15	86.67%
cmd/gindoid/testutils.go	8	12	66.67%
cmd/gindoid/genxml.go	2	7	28.57%
cmd/gindoid/web.go	0	7	0.0%
<!--	Total:	32	50	64.0%	-->

Totals
Change from base Build 1807599398:	0.8%
Covered Lines:	1269
Relevant Lines:	2627

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💛 - Coveralls