Add HTTP::Cookie#destroy

spec/std/http/cookie_spec.cr

@@ -70,6 +70,15 @@ module HTTP
       end
     end
 
+    it "#destroy" do
+      cookie = HTTP::Cookie.new("hello", "world")
+      cookie.destroy
+
+      cookie.value.empty?.should be_true
+      cookie.expired?.should be_true
+      cookie.max_age.should eq(Time::Span.zero)
+    end
+
     describe "#name=" do
       it "raises on invalid name" do
         cookie = HTTP::Cookie.new("x", "")

src/http/cookie.cr

@@ -192,6 +192,16 @@ module HTTP
       end
     end
 
+    # tell the browser to delete the cookie.
+    # Set its value to an empty string
+    # and set its expiration time to the past
+    # Browsers delete cookies that have expired.
+    def destroy
+      self.value = ""
+      self.expires = Time::UNIX_EPOCH
+      self.max_age = Time::Span.zero
+    end
+
     # :nodoc:
     module Parser
       module Regex