Add config option to restrict collection to specific databases

[msmerc]

Right now you can configure the exporter to monitor specific collections, but this is verbose if you want to monitor all the collections but only in a certain database.

Would we add an option to specify the databases to monitor and the exporter could discover all the collections within that database?

[percona-csalguero]

Hello, I think this is a good option and it shouldn't be hard to implement.

[yaron]

you can use wildcards to select all collections in a database. This worked for me to get metrics on all collections in the "yaron" database: --mongodb.collstats-colls=yaron.* --mongodb.indexstats-colls=yaron.*" Maybe this needs to be added to the documentation, but I think this solves the ticket, or am I missing something?