Draft: Support multiple APIs

This MR implements Support new gwdatafind server APIs (#28) by refactoring gwdatafind.api into a subpackage, and implementing a decorator for the gwdatafind.ui methods that selects the xxx_path function from the right API module dynamically.

Also adds a new -A/--api option for the command-line interface.

docs/conf.py

@@ -14,14 +14,14 @@ project = "gwdatafind"
 copyright = "2018-2025, Cardiff University"
 author = "Duncan Macleod"
 release = gwdatafind.__version__
-version = re.split(r'[\w-]', gwdatafind.__version__)[0]
+version = re.split(r"[\w-]", gwdatafind.__version__)[0]
 
 # -- config
 
-source_suffix = '.rst'
-master_doc = 'index'
+source_suffix = ".rst"
+master_doc = "index"
 
-default_role = 'obj'
+default_role = "obj"
 
 # -- theme