Add LndHub service, lnurl-pay endpoints

Enables the lnurl-pay payment workflow

app/controllers/lnurlpay_controller.rb

@@ -0,0 +1,58 @@
+class LnurlpayController < ApplicationController
+  before_action :find_user_by_address
+
+  def index
+    render json: {
+      status: "OK",
+      callback: "https://accounts.kosmos.org/lnurlpay/#{@user.address}/invoice",
+      tag: "payRequest",
+      maxSendable: 1000000,
+      minSendable: 1000,
+      metadata: metadata(@user.address),
+      commentAllowed: 255
+    }
+  end
+
+  def invoice
+    amount = params[:amount].to_i # msats
+    address = params[:address]
+
+    validate_amount(amount)
+
+    # amount = amount / 1000 # we need sats
+    payment_request = @user.ln_create_invoice({
+      amount: amount,
+      description_hash: Digest::SHA2.hexdigest(metadata(address))
+    })
+
+    render json: {
+      status: "OK",
+      successAction: {
+        tag: "message",
+        message: "Payment received. Thanks!"
+      },
+      routes: [],
+      pr: payment_request
+    }
+  end
+
+  private
+
+  def find_user_by_address
+    address = params[:address].split("@")
+    @user = User.where(cn: address.first, ou: address.last).first
+    http_status :not_found if @user.nil?
+  end
+
+  def metadata(address)
+    "[[\"text/identifier\", \"#{address}\"], [\"text/plain\", \"Sats for #{address}\"]]"
+  end
+
+  def validate_amount(amount)
+    if amount > 1000000 || amount < 1000
+      render json: { status: "ERROR", reason: "Invalid amount" }
+      return
+    end
+  end
+
+end