feat(core,admin,testing-tools): core and admin tests

[sdimitris]

Introducing unit testing in core rpc services and admin using jest.

Fix: add 'config' prefix to '/modules' excluded route on Auth.middleware

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other (please describe)

Does this PR introduce a breaking change?

• Yes
• No

The PR fulfills these requirements:

• It's submitted to the main branch
• When resolving a specific issue, it's referenced in the PR's description (e.g. fix #xxx, where "xxx" is the issue number)

[kon14]

Eslint is not parsing this somehow. Run manually.

[kon14]

Tests shouldn't be automatically built together with their corresponding packages as that will increase build times.
We just need tests to be built and run on PRs.

[kkopanidis]

@ChrisPdgn generally looks good I think. 2 points we need to fix: Coverage, and wait for the full release of 0.15

will be addressed post-merge