[monitor, theia] monitor service incorrectly responds with 200 if the request body is malformed

[kittaakos]

Describe the bug

The response ends earlier before setting the 400 status code:

theia-cloud/theia/extensions/monitor-theia/src/node/modules/messaging-backend-module-impl.ts

Lines 22 to 23 in 55813e2

	res.end("Body missing 'level' or 'message' fields");
	res.status(400);

Expected behavior

POST /monitor/message responds with 400 if the request body is invalid

Cluster provider

No response

Version

No response

Additional information

No response