Add ability to read query from file to postgresql_extensible

[buggsdummy]

Feature Request

Opening a feature request kicks off a discussion.

Proposal:

Add ability to pass in parameter to sql file location

Current behavior:

sqlquery="SELECT * FROM pg_stat_database where datname"

Desired behavior:

sqlquery=/var/tmp/sqlfile.sql

Use case:

This would help greatly on servers that have multiple long queries instead of putting it into sqlquery which could get really large

[Zyqsempai]

I can take this one, if the feature is approved.

[danielnelson]

Thanks @Zyqsempai, this would be good to have. I think add a new script option and if both script and sqlquery are set then produce an error:

  [[inputs.postgresql_extensible.query]]
    script = "/var/tmp/sqlfile.sql"