break session user lookup into a util function

src/lib/server/sessionutil.ts

@@ -0,0 +1,19 @@
+import {getDataSource} from './db';
+import {AuthSession} from './entity/AuthSession';
+
+/** Returns the user authorized by a given session. */
+export async function getUserFromSessionID (sessionID: string | undefined) {
+	const dataSource = await getDataSource();
+	const sessionsRepo = dataSource.getRepository(AuthSession);
+	const session = sessionID
+		? await sessionsRepo.findOne({
+			where: {id: sessionID},
+			relations: {
+				authMethod: {
+					user: true,
+				},
+			},
+		})
+		: null;
+	return session?.authMethod.user;
+}