add new function fetch_id() to return a surveyID for a unique survey_name

[markjrieke]

Added a new function fetch_id() that returns a surveyID for a unique survey_name as it appears in the Qualtrics UI (based on the conversation in PR 227). fetch_id() checks that the survey_name is unique, and will throw an error if a non-unique survey_name is passed.

I added a test for fetch_id(). It's not interacting with the API and to keep separate from all_surveys(), the tests are based on a toy dataframe that mimics what all_surveys() currently returns. That may be superfluous (since it's essentially testing error messages & that dplyr::filter and dplyr::pull still function as expected), but I figured it'd be better to have test coverage over the new function than not.

If there are any comments/thoughts/edits, let me know!

[markjrieke]

Ah it looks like the checks are failing due to the lines qualtRics::fetch_id in the test file. The changes pass all tests when I run test_local but similarly fails when I run check() (should have run that prior, but learning as I go here!). I'll get that sorted out locally then push

[juliasilge]

Thank you so much for this contribution @markjrieke! 🙌