DBM related documentation customer feedback

[bryant-bourgeois]

Documentation Page

1. https://docs.datadoghq.com/integrations/postgres/?tab=host#metrics
2. https://docs.datadoghq.com/database_monitoring/setup_postgres/azure/?tab=singleserver#monitoring-relation-metrics-for-multiple-databases

Issue Description

A customer shared some comments about a couple of docs pages when working on a support ticket related to a DBM configuration issue. It seems like this might be the right place to share feedback, though if not, this can be closed. I don't have applicable technical input on the details of changing the docs, just reporting on the customer's behalf.

1. In the metrics table for the postgres integration, there aren't details mentioning if configuration needs to be explicitly applied to collect some of the metrics. The customer would appreciate notes mentioning if any metrics in that table require DBM, and if they require explicit configuration options in DBM to be able to collect those metrics. Perhaps another column in this table would be appropriate.

2. In this header section, it's titled Monitoring relation metrics for multiple databases. The customer was confused, and thought it might suggest that the relations: configuration is only applicable when they're monitoring multiple databases with DBM. Perhaps a solution to clear up this confusion would be a note that the configuration is applicable even when monitoring a single database. Though since the configuration option is applied under a single instance section, that can be deduced, but the customer found it a little confusing.