How to solve "Service name or network name of ... in the PDB is invalid or conflicts with an existing service name or network name in the CDB."

From the alert log during startup of the container database called "cdb":

pdb1(3):***************************************************************
pdb1(3):WARNING: Pluggable Database saes with pdb id - 3 is
pdb1(3):         altered with errors or warnings. Please look into
pdb1(3):         PDB_PLUG_IN_VIOLATIONS view for more details.
pdb1(3):***************************************************************

When I check the PDB_PLUG_IN_VIOLATIONS I see this:

select name,cause,type,message,status,action 
from pdb_plug_in_violations;

NAME	CAUSE	TYPE	MESSAGE	STATUS	ACTION
sales	Service Name Conflict	WARNING	Service name or network name of service salesXDB in the PDB is invalid or conflicts with an existing service name or network name in the CDB.	PENDING	Drop the service and recreate it with an appropriate name.

Check the CDB_SERVICES view:

SELECT name,network_name,creation_date,pdb,enabled
FROM   cdb_services
where con_id=3
and name='salesXDB'
ORDER BY 1;

NAME	NETWORK_NAME	CREATION_DATE	PDB	ENABLED
salesXDB	salesXDB	03/03/2022 11:28:56	sales	NO

There is indeed a service called salesXDB, which is a reminisce from an earlier point in time where "sales" was a non-CDB database.
It has now been replaced with the container database XDB service, in my case called "cdbXDB".

How to address the warnings

Log onto the sales pluggable database:

sqlplus / as sysdba

alter session set container=sales;

Session altered.

Remove the service from the PDB:

exec dbms_service.delete_service('salesXDB');

PL/SQL procedure successfully completed.

If you check the CDB_SERVICES again, it will now be gone.

Restart the pluggable database:

sqlplus / as sysdba

alter session set container=sales;

Session altered.

shutdown immediate
startup

If you query the PDB_PLUG_IN_VIOLATIONS again, you will see that the value for status in the error is now set to RESOLVED:

time	NAME	CAUSE	TYPE	MESSAGE	STATUS	ACTION
11.10.2022 12:49	mvaoppgr	Service Name Conflict	WARNING	Service name or network name of service mvaoppgrXDB in the PDB is invalid or conflicts with an existing service name or network name in the CDB.	RESOLVED	Drop the service and recreate it with an appropriate name.

Source: PDB Name Conflicts With Existing Service Name In The CDB Or The PDB (Doc ID 2247291.1) from Oracle Support