feat(issue-102): add service account token type for gitlab.com accounts

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 84.84848% with 10 lines in your changes missing coverage. Please review.

Project coverage is 88.89%. Comparing base (8942fbd) to head (099001a).

Files	Patch %	Lines
path_token_role.go	45.45%	3 Missing and 3 partials :warning:
gitlab_client.go	91.66%	2 Missing and 2 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #105 +/- ## ========================================== - Coverage 89.16% 88.89% -0.27% ========================================== Files 16 16 Lines 1052 1117 +65 ========================================== + Hits 938 993 +55 - Misses 65 70 +5 - Partials 49 54 +5 ``` | [Flag](https://app.codecov.io/gh/ilijamt/vault-plugin-secrets-gitlab/pull/105/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Ilija+Matoski) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/ilijamt/vault-plugin-secrets-gitlab/pull/105/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Ilija+Matoski) | `88.89% <84.84%> (-0.27%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Ilija+Matoski#carryforward-flags-in-the-pull-request-comment) to find out more.

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[ilijamt]

@GavinCS I was going through the documentation of GitLab and I saw that there are two types of service accounts, one are User Service Accounts (the one that require admin access), and the other ones are Group Service Accounts. Both require at least Premium Tier subscription. At the moment, I don't have access to the subscription. Do you by any chance can help me test on the Premium account or if you can give access to my user, so I can test it?

I created #110 that would allow us to select the proper GitLab type and service account type.

[ilijamt]

I've also asked GitLab Sales if they can provide a license, so I can fully test and develop the service account features. Hopefully they come back with a positive reply.

[GavinCS]

@ilijamt I won't be able to give you access to our Group in Gitlab but I could probably setup an isolated group that we can test with. Gitlab providing a license would be first class - If you gice me the details of your ticket I can also try push with our account manager