TLDR: If you build an SSDT project you can get an error which says:
“SQL71502: Function: [XXX].[XXX] has an unresolved reference to object [XXX].[XXX].”
If the code that is failing is trying to use something in the “sys” schema or the “INFORMATION_SCHEMA” schema then you need to add a database reference to the master dacpac:
Add a database reference to master:
Under the project, right-click References. Select Add database reference….