fix more links and move BackendEntrypoint to the advanced API [skip-ci]

Author: keewis

doc/api-hidden.rst

@@ -826,10 +826,9 @@
    backends.DummyFileManager.acquire_context
    backends.DummyFileManager.close
 
-   backends.common.BackendArray
-   backends.common.BackendEntrypoint
-   backends.common.BackendEntrypoint.guess_can_open
-   backends.common.BackendEntrypoint.open_dataset
+   backends.BackendArray
+   backends.BackendEntrypoint.guess_can_open
+   backends.BackendEntrypoint.open_dataset
 
    core.indexing.IndexingSupport
    core.indexing.explicit_indexing_adapter

doc/api.rst

@@ -890,6 +890,8 @@ Advanced API
    as_variable
    register_dataset_accessor
    register_dataarray_accessor
+   backends.BackendArray
+   backends.BackendEntrypoint
 
 These backends provide a low-level interface for lazily loading data from
 external file-formats or protocols, and can be manually invoked to create

doc/internals/how-to-add-new-backend.rst

@@ -6,7 +6,7 @@ How to add a new backend
 Adding a new backend for read support to Xarray does not require
 to integrate any code in Xarray; all you need to do is:
 
-- Create a class that inherits from Xarray :py:class:`~xarray.backends.common.BackendEntrypoint`
+- Create a class that inherits from Xarray :py:class:`~xarray.backends.BackendEntrypoint`
   and implements the method ``open_dataset`` see :ref:`RST backend_entrypoint`
 
 - Declare this class as an external plugin in your ``setup.py``, see :ref:`RST backend_registration`
@@ -161,8 +161,8 @@ guess_can_open
 ``guess_can_open`` is used to identify the proper engine to open your data
 file automatically in case the engine is not specified explicitly. If you are
 not interested in supporting this feature, you can skip this step since
-:py:class:`~xarray.backends.common.BackendEntrypoint` already provides a
-default :py:meth:`~xarray.backend.common.BackendEntrypoint.guess_can_open`
+:py:class:`~xarray.backends.BackendEntrypoint` already provides a
+default :py:meth:`~xarray.backends.BackendEntrypoint.guess_can_open`
 that always returns ``False``.
 
 Backend ``guess_can_open`` takes as input the ``filename_or_obj`` parameter of
@@ -299,7 +299,7 @@ Where:
 - :py:class:`~xarray.core.indexing.LazilyIndexedArray` is a class
   provided by Xarray that manages the lazy loading.
 - ``MyBackendArray`` shall be implemented by the backend and shall inherit
-  from :py:class:`~xarray.backends.common.BackendArray`.
+  from :py:class:`~xarray.backends.BackendArray`.
 
 BackendArray subclassing
 ^^^^^^^^^^^^^^^^^^^^^^^^