I have federation working perfectly when I use the default values for [queries]
with test data in the mysql database this works.
[queries]
federation = "SELECT username, account_id FROM wp_users WHERE username = ?"
reverse-federation = "SELECT username, account_id FROM wp_users WHERE account_id = ?"

however when I change username to user_login even when the colum in the database does exist and have the same data in it
I get error: Server error: missing destination name user_login

with this [queries] config
[queries]
federation = "SELECT user_login, account_id FROM wp_users WHERE user_login = ?"
reverse-federation = "SELECT user_login, account_id FROM wp_users WHERE account_id = ?"

my temp work around is to temp create an added colum in our database that matches username with the same data as user_login. I took a short look at the code at the point of failure but my C go programing is weak today.

I've attached the mysql.sql that I used to isolate and duplicate this problem
federation_test.sql.zip

Let's discuss whether to add the ability to start https server.

Pros/cons:

• Since we require https for all federation servers it will allow organizations to run it without dealing with nxginx or other proxies.
• Nobody really cares if /federation endpoint is in the root domain. In other words, orgs can start federation server at federation123.example.com subdomain and it will be discoverable using stellar.toml file.
• Most organizations (even smaller ones) use load balancers and it's pretty trivial to forward a specific path to a http server and serve it via https.