As a Metric user I want corrector queries to use DB indexes

[VitaliStupin]

Currently query executed by get_faulty_raw_documents() is slow because it does not use indexes:
https://github.com/nordic-institute/X-Road-Metrics/blob/develop/corrector_module/opmon_corrector/database_manager.py#L110-L118

It can be solved for new installations by adding new index to raw_messages in xroad-metrics-init-mongo:
https://github.com/nordic-institute/X-Road-Metrics/blob/develop/collector_module/opmon_mongodb_maintenance/create_indexes.py#L32

[('corrected', ASC), ('xRequestId', ASC)]

Or by running indexing command manually:

db.raw_messages.createIndex({"corrected": 1, "xRequestId": 1})

Additional notes: If would be great to mention the need to create new indexes in release notes.

[raits]

Hello,

Thank you for the report. We will look into it.