Revert "Removed old semtype decorator"

This reverts commit 80dd2fa.

Author: jtc42

src/labthings/server/decorators.py

@@ -304,6 +304,19 @@ def __call__(self, f):
 tag = Tag
 
 
+class Semtype:
+    def __init__(self, semtype: str):
+        self.semtype = semtype
+
+    def __call__(self, f):
+        # Pass params to call function attribute for external access
+        update_spec(f, {"@type": self.semtype})
+        return f
+
+
+semtype = Semtype
+
+
 class doc_response:
     def __init__(self, code, description=None, mimetype=None, **kwargs):
         self.code = code