RSS DB: schema changes

[aldbr]

User Story

As a diracx developer, I want the RSS database to be streamlined once DIRAC-diracX transition is complete.

Feature Description

The RSS tables currently use the magic string "all" as a server default for
the VO and StatusType columns. This convention was inherited from DIRAC's schema
and must be preserved during the transition because DIRAC reads/writes the same
tables.

After the transition, we should:

1. Add an Alembic migration replacing "all" with NULL in existing rows
2. Change the column server_default from "all" to None
3. Update query logic to treat NULL as "applies to all"
4. Review whether the ElementStatusBase / ElementStatusBaseWithID dual-class hierarchy is still needed (schema.py L24–71). DIRAC uses both composite-PK tables and autoincrement-ID tables; after the transition we may be able to consolidate into a single base class.

Context from PR #857:

• feat: add RSS data models (SQLAlchemy + Pydantic) #857 (comment)
• feat: add RSS data models (SQLAlchemy + Pydantic) #857 (comment)

See whether we still need:

diracx/diracx-db/src/diracx/db/sql/rss/schema.py

Lines 24 to 71 in 4c7853a

	class ElementStatusBase:
	name: Mapped[str64] = mapped_column("Name", primary_key=True)
	status_type: Mapped[str128] = mapped_column(
	"StatusType", server_default="all", primary_key=True
	)
	vo: Mapped[str64] = mapped_column("VO", primary_key=True, server_default="all")
	status: Mapped[str] = mapped_column("Status", String(8), server_default="")
	reason: Mapped[str512] = mapped_column("Reason", server_default="Unspecified")
	date_effective: Mapped[datetime] = mapped_column("DateEffective", SmarterDateTime())
	token_expiration: Mapped[datetime] = mapped_column(
	"TokenExpiration", SmarterDateTime(), server_default="9999-12-31 23:59:59"
	)
	element_type: Mapped[str32] = mapped_column("ElementType", server_default="")
	last_check_time: Mapped[datetime] = mapped_column(
	"LastCheckTime", SmarterDateTime(), server_default="1000-01-01 00:00:00"
	)
	token_owner: Mapped[str] = mapped_column(
	"TokenOwner", String(16), server_default="rs_svc"
	)
	class ElementStatusBaseWithID(ElementStatusBase):
	"""Almost the same as ElementStatusBase.
	Differences:
	- there's an autoincrement ID column which is also the primary key
	- the name and statusType components are not part of the primary key
	"""
	id: Mapped[int] = mapped_column(
	"ID", BigInteger, autoincrement=True, primary_key=True
	)
	name: Mapped[str64] = mapped_column("Name")
	status_type: Mapped[str128] = mapped_column("StatusType", server_default="all")
	vo: Mapped[str64] = mapped_column("VO", server_default="all")
	status: Mapped[str] = mapped_column("Status", String(8), server_default="")
	reason: Mapped[str512] = mapped_column("Reason", server_default="Unspecified")
	date_effective: Mapped[datetime] = mapped_column("DateEffective", SmarterDateTime())
	token_expiration: Mapped[datetime] = mapped_column(
	"TokenExpiration", SmarterDateTime(), server_default="9999-12-31 23:59:59"
	)
	element_type: Mapped[str32] = mapped_column("ElementType", server_default="")
	last_check_time: Mapped[datetime] = mapped_column(
	"LastCheckTime", SmarterDateTime(), server_default="1000-01-01 00:00:00"
	)
	token_owner: Mapped[str] = mapped_column(
	"TokenOwner", String(16), server_default="rs_svc"
	)

Definition of Done

• Alembic migration converts existing "all" values to NULL
• Column defaults updated in SQLAlchemy schema
• Query logic handles NULL semantics
• ElementStatusBase / ElementStatusBaseWithID hierarchy reviewed and simplified if possible
• Tests are written and passing