reorganize code around result formatting

Code is now organized by api version. So formatting has moved to
the api.v1 module. Instead of holding a separate ResultFormatter
object per result format, simply move the functions to the
formater collector and hand in the requested format as a parameter.
Thus reorganized, the api.v1 module can export three simple functions
for result formatting which in turn makes the code that uses
the formatters much simpler.

nominatim/api/v1/format.py

@@ -0,0 +1,38 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# This file is part of Nominatim. (https://nominatim.org)
+#
+# Copyright (C) 2023 by the Nominatim developer community.
+# For a full list of authors see the git log.
+"""
+Output formatters for API version v1.
+"""
+from typing import Dict, Any
+from collections import OrderedDict
+import json
+
+from nominatim.api.result_formatting import FormatDispatcher
+from nominatim.api import StatusResult
+
+dispatch = FormatDispatcher()
+
+@dispatch.format_func(StatusResult, 'text')
+def _format_status_text(result: StatusResult) -> str:
+    if result.status:
+        return f"ERROR: {result.message}"
+
+    return 'OK'
+
+
+@dispatch.format_func(StatusResult, 'json')
+def _format_status_json(result: StatusResult) -> str:
+    out: Dict[str, Any] = OrderedDict()
+    out['status'] = result.status
+    out['message'] = result.message
+    if result.data_updated is not None:
+        out['data_updated'] = result.data_updated.isoformat()
+    out['software_version'] = str(result.software_version)
+    if result.database_version is not None:
+        out['database_version'] = str(result.database_version)
+
+    return json.dumps(out)