add types package

This package will contain all the parameter types that need parsing from
the outside world into internal types.

Each type is required to implement its own UnmarshalJSON. At this point
it should also make the checks, if the incoming data is valid input, but
is not required to check against the database.

types/zone.go

@@ -0,0 +1,20 @@
+package types
+
+import (
+	"bytes"
+	"fmt"
+)
+
+type (
+	Zone string
+)
+
+func (z *Zone) UnmarshalJSON(in []byte) error {
+	in = bytes.Trim(in, `"`)
+
+	if in[len(in)-1] != '.' {
+		return fmt.Errorf("not a valid zone name")
+	}
+	*z = Zone(in)
+	return nil
+}