SQLPackage - Synapse Serverless Support for Role Membership

This issue ported from https://feedback.azure.com/d365community/idea/e00d13dc-edbe-ed11-a81b-00224850345d

Really excited for the new capability to use SQLPackage with Synapse Serverless and just finished testing some Extracting and Publishing into an instance that is not more than a month old.  Ran into an error trying to replicate Role Memberships that I think may be related to a system stored procedure sp_addrolemember that is available elsewhere but not in Synapse Serverless.   I propose that SQLPackage team implement "ALTER ROLE" syntax like

ALTER ROLE [db_datareader] ADD MEMBER [someuser]

when publishing to Synapse or the Synapse Serverless team implement sp_addrolemember. 

Here is what the error looked like in SQLPackage against a Synapse Serverless Instance
Msg 15871, Level 16, State 4, Procedure sp_addrolemember, Line 1 [Batch Start Line 0]
PROCEDURE 'sp_addrolemember' is not supported.
EXECUTE sp_addrolemember @rolename = N'db_datareader', @membername = N'someuser';