WIP: add new backend api documentation (#4810)

* documentation first draft

* documentation update

* documentation update

* update documentation

* update backend documentation

* incompletre draft: update Backend Documentation

* fix

* fix syle

* Update doc/internals.rst

Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: Mathias Hauser <mathause@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: keewis <keewis@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: Mathias Hauser <mathause@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: Mathias Hauser <mathause@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: Mathias Hauser <mathause@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: Mathias Hauser <mathause@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: Mathias Hauser <mathause@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: keewis <keewis@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: keewis <keewis@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: Mathias Hauser <mathause@users.noreply.github.com>

* update section lazy laoding

* Update doc/internals.rst

Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>

* Update doc/internals.rst

Co-authored-by: keewis <keewis@users.noreply.github.com>

* update internals.rst backend

* add lazy loading documentation

* update example on indexing type

* style

* fix

* modify backend indexing doc

* fix

* removed LazilyVectorizedIndexedArray from backend doc

* small fix in doc

* small fixes in backend doc

* removed exmple vectorized indexing

* update documentation

* update documentation

* isort

* rename store_spec in filename_or_obj in guess_can_open

* small update in backend documentation

* small update in backend documentation

* Update doc/internals.rst

Co-authored-by: Stephan Hoyer <shoyer@google.com>

* Update doc/internals.rst

Co-authored-by: Stephan Hoyer <shoyer@google.com>

* fix backend documentation

* replace LazilyOuterIndexedArray with LazilyIndexedArray

* Update doc/internals.rst

Co-authored-by: Julia Dark <github@email.jpdark.com>

* Update doc/internals.rst

Co-authored-by: Julia Dark <github@email.jpdark.com>

* Fix broken doc merge

Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>
Co-authored-by: Mathias Hauser <mathause@users.noreply.github.com>
Co-authored-by: keewis <keewis@users.noreply.github.com>
Co-authored-by: Stephan Hoyer <shoyer@google.com>
Co-authored-by: Julia Dark <github@email.jpdark.com>
Co-authored-by: Alessandro Amici <a.amici@bopen.eu>

doc/api-hidden.rst

@@ -811,3 +811,28 @@
    backends.DummyFileManager.acquire
    backends.DummyFileManager.acquire_context
    backends.DummyFileManager.close
+
+   backends.common.BackendArray
+   backends.common.BackendEntrypoint
+   backends.common.BackendEntrypoint.guess_can_open
+   backends.common.BackendEntrypoint.open_dataset
+
+   core.indexing.IndexingSupport
+   core.indexing.explicit_indexing_adapter
+   core.indexing.BasicIndexer
+   core.indexing.OuterIndexer
+   core.indexing.VectorizedIndexer
+   core.indexing.LazilyIndexedArray
+   core.indexing.LazilyVectorizedIndexedArray
+
+   conventions.decode_cf_variables
+
+   coding.variables.UnsignedIntegerCoder
+   coding.variables.CFMaskCoder
+   coding.variables.CFScaleOffsetCoder
+
+   coding.strings.CharacterArrayCoder
+   coding.strings.EncodedStringCoder
+
+   coding.times.CFTimedeltaCoder
+   coding.times.CFDatetimeCoder