Remove single-model registration from PluginTemplateExtension #18072
Description
Proposed Changes
Drop support for registering a single model with a PluginTemplateExtension subclass via the model attribute.
Justification
Model assignment is now done through the models (plural) attribute, which accepts an iterable of one or more models (see #17029)
Impact
Any plugins which employ PluginTemplateExtension subclasses will need to be slightly modified to support NetBox v4.3. See #17029 for implementation details.