Add method get_tstds

[stefanbschneider]

Similar to how the project module provides a method get_nsds and get_vnfds, it should also provide a method get_tstds to return all included test descriptors based on their MIME type application/vnd.5gtango.tstd.

• [x] Fork the repo, create a new branch dev and do all the following steps in this fork and branch
• [x] Adjust the example project with an example test descriptor
• [x] Ensure the test descriptor is listed correctly in the project.yml with MIME type application/vnd.5gtango.tstd and tag eu.tango.
• [x] Implement get_tstds to return the test descriptor (in a list)
• [x] To test if the method works, create a new module test_project_unit.py in the tests directory using pytest tests
  • [x] Load the example-project using Project.load_project. Assert the project was loaded correctly
  • [x] Create a unit test for testing the existing get_vnfds and get_nsds. Assert the methods return lists of the VNFDs and NSD in the project
  • [x] Once this works, write a test for your get_tstds method. Assert that it returns a list with the relative file path to the added test descriptor. Also test if it works correctly without any test descriptor, by temporarily removing the test descriptor from the example project.

@anapolg @MiguelRivasQuobis

[stefanbschneider]

@anapolg @MiguelRivasQuobis the issue was just implemented and merged :)