feat(point): specify tags as a NamedTuple

spec/influx_db/line_protocol_spec.cr

@@ -17,7 +17,7 @@ describe InfluxDB::LineProtocol do
 
     it "serializes when tags are present" do
       point = InfluxDB::Point.new "foo", time, a: 1
-      point.tag :test, "bar"
+      point.tag test: "bar"
       InfluxDB::LineProtocol.serialize(point).should eq("foo,test=bar a=1 #{ts}")
     end
   end

spec/influx_db/point_spec.cr

@@ -29,7 +29,7 @@ describe InfluxDB::Point do
   describe "#tag" do
     it "allows tagging of points" do
       point = InfluxDB::Point["foo", a: 1]
-      point.tag :test, "bar"
+      point.tag test: "bar"
       point.tags.should eq({:test => "bar"})
     end
   end
@@ -39,7 +39,7 @@ describe InfluxDB::Point do
       time = Time.utc
       ts = time.to_unix
       point = InfluxDB::Point.new "foo", time, a: 1
-      point.tag :test, "bar"
+      point.tag test: "bar"
       point.to_s.should eq("foo,test=bar a=1 #{ts}")
     end
   end

src/influx_db/point.cr

@@ -28,9 +28,11 @@ struct InfluxDB::Point
     {% end %}
   end
 
-  # Append or change a tag on the point.
-  def tag(key, value)
-    tags[key] = value
+  # Append or change tags associated with the point.
+  def tag(**t : **T) forall T
+    {% for k in T %}
+      tags[{{k.symbolize}}] = t[{{k.symbolize}}]
+    {% end %}
   end
 
   # Checks if any tags are defined for the point.