refactor: PgArg to ProcParam

Clarify the difference between arguments and parameters.
Parameters are part of the function definition, arguments are the values
passed to the function.

Also clarify the findProc function comments and error message.

src/PostgREST/OpenAPI.hs

@@ -27,8 +27,8 @@ import PostgREST.Config                   (AppConfig (..), Proxy (..),
                                            isMalformedProxyUri, toURI)
 import PostgREST.DbStructure              (DbStructure (..),
                                            tableCols, tablePKCols)
-import PostgREST.DbStructure.Proc         (PgArg (..),
-                                           ProcDescription (..))
+import PostgREST.DbStructure.Proc         (ProcDescription (..),
+                                           ProcParam (..))
 import PostgREST.DbStructure.Relationship (Cardinality (..),
                                            PrimaryKey (..),
                                            Relationship (..))
@@ -130,11 +130,11 @@ makeProcSchema pd =
   (mempty :: Schema)
   & description .~ pdDescription pd
   & type_ ?~ SwaggerObject
-  & properties .~ fromList (fmap makeProcProperty (pdArgs pd))
-  & required .~ fmap pgaName (filter pgaReq (pdArgs pd))
+  & properties .~ fromList (fmap makeProcProperty (pdParams pd))
+  & required .~ fmap ppName (filter ppReq (pdParams pd))
 
-makeProcProperty :: PgArg -> (Text, Referenced Schema)
-makeProcProperty (PgArg n t _ _) = (n, Inline s)
+makeProcProperty :: ProcParam -> (Text, Referenced Schema)
+makeProcProperty (ProcParam n t _ _) = (n, Inline s)
   where
     s = (mempty :: Schema)
           & type_ ?~ toSwaggerType t