fix: not logging the JSON message on a PGRST002 error

It happens right after the configuration is loaded and before
the schema cache is queried.

src/PostgREST/App.hs

@@ -126,11 +126,14 @@ postgrestResponse
   -> Wai.Request
   -> Handler IO Wai.Response
 postgrestResponse appState conf@AppConfig{..} maybeSchemaCache authResult@AuthResult{..} req = do
+  let observer = AppState.getObserver appState
+
   sCache <-
     case maybeSchemaCache of
       Just sCache ->
         return sCache
-      Nothing ->
+      Nothing -> do
+        lift $ observer SchemaCacheEmptyObs
         throwError Error.NoSchemaCacheError
 
   body <- lift $ Wai.strictRequestBody req
@@ -144,7 +147,6 @@ postgrestResponse appState conf@AppConfig{..} maybeSchemaCache authResult@AuthRe
 
   let mainQ = Query.mainQuery plan conf apiReq authResult configDbPreRequest
       tx = MainTx.mainTx mainQ conf authResult apiReq plan sCache
-      observer = AppState.getObserver appState
       obsQuery s = when configLogQuery $ observer $ QueryObs mainQ s
 
   (txTime, txResult) <- withTiming $ do

src/PostgREST/Logger.hs

@@ -95,6 +95,9 @@ observationLogger loggerState logLevel obs = case obs of
   o@(QueryErrorCodeHighObs _) -> do
     when (logLevel >= LogError) $ do
       logWithZTime loggerState $ observationMessage o
+  o@SchemaCacheEmptyObs ->
+    when (logLevel >= LogError) $ do
+    logWithZTime loggerState $ observationMessage o
   o@(HasqlPoolObs _) -> do
     when (logLevel >= LogDebug) $ do
       logWithZTime loggerState $ observationMessage o

src/PostgREST/Observation.hs

@@ -37,6 +37,7 @@ data Observation
   | ExitDBNoRecoveryObs
   | ExitDBFatalError ObsFatalError SQL.UsageError
   | DBConnectedObs Text
+  | SchemaCacheEmptyObs
   | SchemaCacheErrorObs (NonEmpty Text) [Text] SQL.UsageError
   | SchemaCacheQueriedObs Double
   | SchemaCacheSummaryObs Text
@@ -88,6 +89,8 @@ observationMessage = \case
     "If you are using connection poolers in transaction mode, try setting db-prepared-statements to false. " <> jsonMessage usageErr
   ExitDBFatalError ServerError08P01 usageErr ->
     "Connection poolers in statement mode are not supported." <> jsonMessage usageErr
+  SchemaCacheEmptyObs ->
+    T.decodeUtf8 . LBS.toStrict . Error.errorPayload $ Error.NoSchemaCacheError
   SchemaCacheErrorObs dbSchemas extraPaths usageErr ->
     "Failed to load the schema cache using "
       <> "db-schemas=" <> T.intercalate "," (toList dbSchemas)