sqlc: introduce NewForType helper method

The upcoming implementation of `sqldb/v2` will extensively create
a `Queries` object on the fly. To make more intuitive how to create
the queries object for specific database types, we introduce a
`NewForType` helper method.
This also mimics how `tapd` creates the `Queries` object, and in order
not let `litd` have it's own definition of how `Queries` object are
created on the fly, the upcoming `sqldb/v2` usage will utilize this
helper method.

Author: ViktorTigerstrom

db/sqlc/db_custom.go

@@ -36,6 +36,11 @@ func NewPostgres(db DBTX) *Queries {
 	return &Queries{db: &wrappedTX{db, sqldb.BackendTypePostgres}}
 }
 
+// NewForType creates a new Queries instance for the given database type.
+func NewForType(db DBTX, typ sqldb.BackendType) *Queries {
+	return &Queries{db: &wrappedTX{db, typ}}
+}
+
 // CustomQueries defines a set of custom queries that we define in addition
 // to the ones generated by sqlc.
 type CustomQueries interface {