Keep the API user agent reading the deployed version

Go back to building the user agent from deployed_version.txt instead of a
hard coded version number. The deployed version stamp already tells the
logs which build made each call, so a separate release number is not
needed.

Author: christophervoelpel

common.py

@@ -126,11 +126,6 @@ class TrackingType(enum.Enum):
 
 _USER_AGENT_PREFIX = 'cloud-solutions/mas-scenemachine'
 
-# Released application version, surfaced in the API user-agent so Google Cloud
-# logs attribute calls to a clean "scene-machine v1" instead of the deploy stamp
-# (branch + timestamp) that deployed_version.txt holds. Bump on a release.
-VERSION = '1.0.0'
-
 
 @functools.lru_cache(maxsize=None)
 def get_api_client_headers(tracking_type: TrackingType) -> dict[str, str]:
@@ -145,7 +140,12 @@ def get_api_client_headers(tracking_type: TrackingType) -> dict[str, str]:
     A dictionary of headers.
   """
 
-  user_agent = f'{_USER_AGENT_PREFIX}-{tracking_type.value}-v{VERSION}'
+  user_agent = f'{_USER_AGENT_PREFIX}-{tracking_type.value}-v'
+  try:
+    with open('deployed_version.txt', 'r') as f:
+      user_agent += f.read().strip()
+  except FileNotFoundError:
+    user_agent += 'unknown'
 
   return {
       'User-Agent': user_agent,