Feat: backend supports with cookies

src/invidious/routes/switch_backend.cr

@@ -0,0 +1,18 @@
+{% skip_file if flag?(:api_only) %}
+
+module Invidious::Routes::BackendSwitcher
+  def self.switch(env)
+    referer = get_referer(env)
+    backend_id = env.params.query["backend_id"]
+
+    # Checks if there is any alternative domain, like a second domain name,
+    # TOR or I2P address
+    if alt = CONFIG.alternative_domains.index(env.request.headers["Host"])
+      env.response.cookies["SERVER_ID"] = Invidious::User::Cookies.server_id(CONFIG.alternative_domains[alt], backend_id)
+    else
+      env.response.cookies["SERVER_ID"] = Invidious::User::Cookies.server_id(CONFIG.domain, backend_id)
+    end
+
+    env.redirect referer
+  end
+end