[pcu-group] - Add a flag to define the pcu group when creating a DB

[clun]

Description

The Astra CLI doesn’t support PCU group assignment with database creation. To add a database to a PCU group during database creation, you must use the DevOps API or Astra Portal to create the database.

astra db create mydb \
  --pcu-group PCU_GROUP_ID

• The devops API will now allow this flag in DB Creation Request