Datasource-http-backend: Delete unused server code and update documentation #1407

Job	Run time
setup-matrix	8s
run-integration-tests (./examples/app-with-backend)	3m 18s
run-integration-tests (./examples/panel-datalinks)	2m 51s
run-integration-tests (./examples/datasource-basic)	4m 14s
run-integration-tests (./examples/app-with-rbac)	2m 18s
run-integration-tests (./examples/app-with-scenes)	1m 38s
run-integration-tests (./examples/datasource-streaming-websocket/streaming-websocket-plugin)	1m 40s
run-integration-tests (./examples/app-basic)	2m 57s
run-integration-tests (./examples/panel-frame-select)	3m 12s
run-integration-tests (./examples/datasource-streaming-backend-websocket/streaming-backend-websoc...	2m 16s
run-integration-tests (./examples/datasource-http)	2m 54s
run-integration-tests (./examples/datasource-http-backend)	4m 36s
run-integration-tests (./examples/app-with-extensions)	2m 58s
run-integration-tests (./examples/app-with-extension-point)	2m 34s
run-integration-tests (./examples/app-with-service-account)	2m 22s
run-integration-tests (./examples/app-with-dashboards)	3m 5s
run-integration-tests (./examples/panel-basic)	2m 57s
run-integration-tests (./examples/datasource-logs)	1m 33s
notify	0s
	47m 31s

Provide feedback