Get rid of DirectThingClient and friends.

This gets rid of a bunch of now-obsolete code that used dependencies for inter-thing communication. The new `lt.thing_slot` system does this much better.

This required removing a section of the docs and its example code, as that was being tested. That's helpful, as said section detailed the features I'm removing.

I have retained the `_dependencies` reference in Sphinx but moved it to a new section on removed features: this should help redirect people to how the code has changed.

Author: rwb27

docs/source/dependencies/dependencies.rst

@@ -12,13 +12,13 @@ Documentation for LabThings-FastAPI
    properties.rst
    documentation.rst
    thing_slots.rst
-   dependencies/dependencies.rst
    blobs.rst
    concurrency.rst
    using_things.rst
    see_also.rst
    examples.rst
    wot_core_concepts.rst
+   removed_features.rst
 
    autoapi/index
    developer_notes/index.rst

docs/source/dependencies/example.py

@@ -0,0 +1,8 @@
+Removed Features
+================
+
+.. _dependencies:
+
+Dependencies
+------------
+The use of dependencies for inter-`.Thing` communication was removed in version 0.1. See :ref:`thing_slots` and `.ThingServerInterface` for a more intuitive way to access that functionality.

docs/source/index.rst

@@ -25,7 +25,6 @@
 from .properties import property, setting, DataProperty, DataSetting
 from .actions import action
 from .endpoints import endpoint
-from . import deps
 from . import outputs
 from .outputs import blob
 from .server import ThingServer, cli
@@ -53,7 +52,6 @@
     "action",
     "thing_slot",
     "endpoint",
-    "deps",
     "outputs",
     "blob",
     "ThingServer",