don't surface SQL error messages in graphql

test plan:
 - undo this fix locally:
   https://gerrit.instructure.com/c/canvas-lms/+/358062/6/app/models/conversation.rb
 - attempt to send a conversation message
 - the graphql call should result in a 500 error and the invalid SQL
   should show up in /error_reports and not the browser console

flag=none
closes FOO-4874

Change-Id: I78686a28ce3c99d2137f35423dbd81fe5e833658
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/360950
Reviewed-by: Keith Garner <kgarner@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: August Thornton <august@instructure.com>
QA-Review: Jeremy Stanley <jeremy@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>

app/graphql/graphql_postgres_timeout.rb

@@ -39,7 +39,7 @@ module GraphQLPostgresTimeout
           end
           raise GraphQLPostgresTimeout::Error, "operation timed out"
         end
-        raise GraphQL::ExecutionError, "Invalid SQL: #{e.message}"
+        raise
       end
     end
   end

spec/graphql/postgres_statement_timeout_spec.rb

@@ -55,5 +55,10 @@ describe "graphql pg statement_timeouts" do
       expect(result.dig("data", "updateAssignment")).to be_nil
       expect(result.dig("errors", 0, "path")).to eq ["updateAssignment"]
     end
+
+    it "does not surface other StatementInvalid exception details" do
+      allow(Assignment).to receive(:find) { raise ActiveRecord::StatementInvalid, "not a timeout" }
+      expect { CanvasSchema.execute(mutation, context: { current_user: @teacher }) }.to raise_error("not a timeout")
+    end
   end
 end