Create project_contacts test: for tags; different array PIs, same project

[mhpob]

Add a row or rows with a duplicate detectedby code and a different set of PIs. Test for correct outcome -- that the PIs are combined within a detectedby code and the data are summarized by unique detectedby code.

See #11 for context.

Coverage aim: https://app.codecov.io/gh/mhpob/otndo/blob/main/R%2Fproject_contacts.R#L76
Current test file: https://github.com/mhpob/otndo/blob/main/tests/testthat/test-project_contacts.R