Pass `ctx.self_program_id` from `ProgramContext` into `initialize_account`
and `mint`, which now assert that the token definition account is owned by
the token program. This prevents callers from supplying a foreign-owned
account as the definition.
See https://github.com/logos-co/spel/issues/172
This updates the spel dependency, which introduces a breaking change.
To make reviewing changes easier from other changes, this update comes
in a separate commit.
