Add support for learning sites in DB

[joekr]

We should create a DB table to pull the learning site info dynamically. This will allow us to add new sites to pull and which channels to post to.

We should be able to leverage the same TF config as the learning_table oci_nosql_table. Then make the learning function query the new table on invocation instead of using the learning_sites_rss list.

[xtoddx]

Should this be closed, or is there more work you're hoping to do, @joekr ?

[joekr]

Right now it still reads a local file. I would love to dynamically pull the sites on each run from the DB.