Deploy with db_owner and DropObjectsNotInSource option user drops the user in target

- SqlPackage or DacFx Version:
- .NET Framework (Windows-only) or .NET Core:
- Environment (local platform and source/target platforms):

**Steps to Reproduce:**

1. Create a db with a table t1 and with a db_owner user on a login
2. Create another database with only a table (t2) and extract to a dacpac
3. using sqlpcakge publish the dacpac from step 2 to the database in step 1. use the new user in the db in sqlpackage.exe publish command. set option DropObjectsNotInSource to true

Expected: Database 1 should have table t1 dropped and t2 created
Actual: the user in database 1 is dropped to it cannot continue with the publish

**Did this occur in prior versions? If not - which version(s) did it work in?**

(DacFx/SqlPackage/SSMS/Azure Data Studio)

Start by reproducing the issue with SqlPackage publish, a dacpac containing table t2, DropObjectsNotInSource enabled, and the db_owner user described in the steps. Compare the publish behavior with the expected handling of the existing user and tables; done means the publish completes without dropping the user unexpectedly.

Written by the indexing model from the issue text.