Refactor dsi redirect in omniauth

We need the dsi redirect to be more flexible, to allow more hosts to
user DFE sign in so this commit just gets the base url from the request
i.e. http://host:port and we can append `auth/dfe/callback` to it.

config/initializers/omniauth.rb

@@ -31,12 +31,10 @@
   end
 
   SETUP_PROC = lambda do |env|
-    service = HostingEnvironment.current_service(Rack::Request.new(env))
+    request = Rack::Request.new(env)
+    service = HostingEnvironment.current_service(request)
 
-    dfe_sign_in_redirect_uri = URI.join(
-      HostingEnvironment.application_url(service),
-      "/auth/dfe/callback",
-    )
+    dfe_sign_in_redirect_uri = URI.join(request.base_url, "/auth/dfe/callback")
 
     env["omniauth.strategy"].options.client_options = {
       port: dfe_sign_in_issuer_uri&.port,

lib/hosting_environment.rb

@@ -14,11 +14,6 @@ module HostingEnvironment
     placements: ENV["PLACEMENTS_DFE_SIGN_IN_SECRET"],
   }.with_indifferent_access.freeze
 
-  SERVICE_HOST = {
-    claims: ENV["CLAIMS_HOST"],
-    placements: ENV["PLACEMENTS_HOST"],
-  }.with_indifferent_access.freeze
-
   def self.env
     @env ||= ActiveSupport::EnvironmentInquirer.new(ENV["HOSTING_ENV"].presence || "development")
   end
@@ -39,14 +34,6 @@ def self.dfe_sign_in_secret(current_service)
     DFE_SIGN_IN_CLIENT_SECRETS.fetch(current_service)
   end
 
-  def self.application_url(current_service)
-    if Rails.env.development?
-      "http://#{SERVICE_HOST.fetch(current_service)}:#{ENV.fetch("PORT", 3000)}"
-    else
-      "https://#{SERVICE_HOST.fetch(current_service)}"
-    end
-  end
-
   def self.current_service(request)
     case request.host
     when ENV["CLAIMS_HOST"], *ENV.fetch("CLAIMS_HOSTS", "").split(",")

spec/lib/hosting_environment_spec.rb

@@ -88,42 +88,6 @@
     end
   end
 
-  describe ".application_url" do
-    it "returns the application url for claims" do
-      current_service = "claims"
-      expect(described_class.application_url(current_service)).to eq(
-        "https://claims.localhost",
-      )
-    end
-
-    it "returns the application url for placements" do
-      current_service = "placements"
-      expect(described_class.application_url(current_service)).to eq(
-        "https://placements.localhost",
-      )
-    end
-
-    context "when env is development" do
-      it "returns the application url for claims with port" do
-        allow(Rails.env).to receive(:development?).and_return(true)
-        current_service = "claims"
-
-        expect(described_class.application_url(current_service)).to eq(
-          "http://claims.localhost:3000",
-        )
-      end
-
-      it "returns the application url for placements with port" do
-        allow(Rails.env).to receive(:development?).and_return(true)
-        current_service = "placements"
-
-        expect(described_class.application_url(current_service)).to eq(
-          "http://placements.localhost:3000",
-        )
-      end
-    end
-  end
-
   describe ".current_service" do
     it "returns the current service for claims" do
       request = instance_double("Rack::Request", host: ENV["CLAIMS_HOST"])