Adding new metric data for PostgreSQL

The Metric API is a way to get metric data from AWS PostgreSQL RDS into New Relic dashboards. A metric means a numeric measurement of an application, a system, or a database. Metrics are typically reported on a regular schedule. There are two types of metrics:  

• Aggregated data: the rate of some event per minute
• A numeric status at a moment in time: for example, the CPU% used status

Metrics are a strong solution for monitoring dashboards. The metrics that are used in New Relic are as follows:

• readIops: This measures the average number of disk I/O operations per second.
• writeIops: This measures the average number of disk I/O operations per second.
• databaseConnections: This measures the number of connections to an instance.
• cpuUtilization: This measures the percentage of CPU used by a DB instance.
• readLatency: This measures the average amount of time taken per disk I/O operation, in seconds.
• writeLatency:&...