add deprecation warnings in the code

CMakeLists.txt

@@ -271,3 +271,7 @@ if (INSTALL_MUNIN_PLUGINS)
                   munin/nominatim_requests
             DESTINATION ${NOMINATIM_MUNINDIR})
 endif()
+
+message(WARNING "Building with CMake is deprecated and will be removed in Nominatim 5.0."
+                "Use Nominatim pip packages instead.\n"
+                "See https://nominatim.org/release-docs/develop/admin/Installation/#downloading-and-building-nominatim")

src/nominatim_db/cli.py

@@ -119,7 +119,13 @@ def run(self, **kwargs: Any) -> int:
         log.warning('Using project directory: %s', str(args.project_dir))
 
         try:
-            return args.command.run(args)
+            ret = args.command.run(args)
+
+            if args.config.TOKENIZER == 'legacy':
+                log.warning('WARNING: the "legacy" tokenizer is deprecated '
+                            'and will be removed in Nominatim 5.0.')
+
+            return ret
         except UsageError as exception:
             if log.isEnabledFor(logging.DEBUG):
                 raise # use Python's exception printing
@@ -169,6 +175,8 @@ def run(self, args: NominatimArgs) -> int:
         if args.engine == 'php':
             if args.config.lib_dir.php is None:
                 raise UsageError("PHP frontend not configured.")
+            LOG.warning('\n\nWARNING: the PHP frontend is deprecated '
+                        'and will be removed in Nominatim 5.0.\n\n')
             run_php_server(args.server, args.project_dir / 'website')
         else:
             asyncio.run(self.run_uvicorn(args))

src/nominatim_db/tokenizer/legacy_tokenizer.py

@@ -38,10 +38,12 @@
 def create(dsn: str, data_dir: Path) -> 'LegacyTokenizer':
     """ Create a new instance of the tokenizer provided by this module.
     """
+    LOG.warning('WARNING: the legacy tokenizer is deprecated '
+                'and will be removed in Nominatim 5.0.')
     return LegacyTokenizer(dsn, data_dir)
 
 
-def _install_module(config_module_path: str, src_dir: Path, module_dir: Path) -> str:
+def _install_module(config_module_path: str, src_dir: Optional[Path], module_dir: Path) -> str:
     """ Copies the PostgreSQL normalisation module into the project
         directory if necessary. For historical reasons the module is
         saved in the '/module' subdirectory and not with the other tokenizer
@@ -55,6 +57,10 @@ def _install_module(config_module_path: str, src_dir: Path, module_dir: Path) ->
         LOG.info("Using custom path for database module at '%s'", config_module_path)
         return config_module_path
 
+    # Otherwise a source dir must be given.
+    if src_dir is None:
+        raise UsageError("The legacy tokenizer cannot be used with the Nominatim pip module.")
+
     # Compatibility mode for builddir installations.
     if module_dir.exists() and src_dir.samefile(module_dir):
         LOG.info('Running from build directory. Leaving database module as is.')