feat: add invitation get by id endpoint
Description
get invitation by id.
Related issues
Testing
Checklist
-
I have updated the documentation (if necessary) -
I have added unit tests for new functionality (if applicable) -
My code follows the style guidelines of this project -
I have tested this code on my local machine before submitting this MR
Reviewers
Additional Notes
Closes #68 (closed)
Edited by Zdravko Iliev