feat: keep a reference to the credentials in the config

[moritzraho]

Description

Currently there is no way to know if the credentials belong to the workspace or not and what is the integration id.
This PR adds the credentials reference and id into the workspace config so that the credentials can be retrieved from the .env using that key

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov]

Codecov Report

Merging #253 into master will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #253   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           21        21           
  Lines          773       775    +2     
  Branches       106       106           
=========================================
+ Hits           773       775    +2     

Impacted Files	Coverage Δ
src/lib/import.js	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 348f3ea...60c7452. Read the comment docs.