fix(db): add additional connection pool for projection spooling (#7094)

* fix(db): add additional connection pool for projection spooling

* use correct connection pool for projections

---------

Co-authored-by: Livio Spring <livio.a@gmail.com>

internal/database/dialect/config.go

@@ -23,8 +23,37 @@ type Matcher interface {
 	Decode([]interface{}) (Connector, error)
 }
 
+const (
+	QueryAppName             = "zitadel_queries"
+	EventstorePusherAppName  = "zitadel_es_pusher"
+	ProjectionSpoolerAppName = "zitadel_projection_spooler"
+	defaultAppName           = "zitadel"
+)
+
+// DBPurpose is what the resulting connection pool is used for.
+type DBPurpose int
+
+const (
+	DBPurposeQuery DBPurpose = iota
+	DBPurposeEventPusher
+	DBPurposeProjectionSpooler
+)
+
+func (p DBPurpose) AppName() string {
+	switch p {
+	case DBPurposeQuery:
+		return QueryAppName
+	case DBPurposeEventPusher:
+		return EventstorePusherAppName
+	case DBPurposeProjectionSpooler:
+		return ProjectionSpoolerAppName
+	default:
+		return defaultAppName
+	}
+}
+
 type Connector interface {
-	Connect(useAdmin, isEventPusher bool, pusherRatio float32, appName string) (*sql.DB, error)
+	Connect(useAdmin bool, pusherRatio, spoolerRatio float64, purpose DBPurpose) (*sql.DB, error)
 	Password() string
 	Database
 }