Only support primary domain for Lightning Address

Part of the process of removing support for serving multiple domains
from a single akkounts instance.

Also puts the Lightning Address discovery routes under the .well-known
path. Combined, these changes simplify reverse-proxying to the
.well-known endpoints.

config/routes.rb

@@ -56,14 +56,12 @@ Rails.application.routes.draw do
     end
   end
 
-  get 'lnurlpay/:address', to: 'lnurlpay#index',
-    as: 'lightning_address', constraints: { address: /[^\/]+/}
-  get 'lnurlpay/:address/invoice', to: 'lnurlpay#invoice',
-    as: 'lnurlpay_invoice', constraints: { address: /[^\/]+/}
-  get 'keysend/:address', to: 'lnurlpay#keysend',
-    as: 'lightning_address_keysend', constraints: { address: /[^\/]+/}
-
+  get '.well-known/webfinger', to: 'webfinger#show'
   get '.well-known/nostr', to: 'well_known#nostr'
+  get '.well-known/lnurlpay/:username', to: 'lnurlpay#index', as: 'lightning_address'
+  get '.well-known/keysend/:username', to: 'lnurlpay#keysend', as: 'lightning_address_keysend'
+
+  get 'lnurlpay/:username/invoice', to: 'lnurlpay#invoice', as: 'lnurlpay_invoice'
 
   post 'webhooks/lndhub', to: 'webhooks#lndhub'
 
@@ -96,8 +94,6 @@ Rails.application.routes.draw do
     }, controller: 'oauth'
   end
 
-  get '.well-known/webfinger', to: 'webfinger#show'
-
   namespace :discourse do
     get "connect", to: 'sso#connect'
   end