(Chore) GoodID API unit tests & fixes

[johnsmith-gooddollar]

Description

• added unit tests for issue location certificate endpoint
• added unit tests for verify location certificate endpoint
• bugfixes
• TODO: Solve Error: invalid_setup: your agent does not seem to have ICredentialIssuerLD plugin installed

About #459

Checklist:

• PR title matches follow: (Feature|Bug|Chore) Task Name
• My code follows the style guidelines of this project
• I have followed all the instructions described in the initial task (check Definitions of Done)
• I have performed a self-review of my own code
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have added reference to a related issue in the repository
• I have added a detailed description of the changes proposed in the pull request. I am as descriptive as possible, assisting reviewers as much as possible.
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