Add form examples to plugin dev docs

docs/plugins/development/forms.md

@@ -4,17 +4,145 @@
 
 NetBox provides several base form classes for use by plugins.
 
-* `NetBoxModelForm`
+| Form Class                | Purpose                              |
-* `NetBoxModelCSVForm`
+|---------------------------|--------------------------------------|
-* `NetBoxModelBulkEditForm`
+| `NetBoxModelForm`         | Create/edit individual objects       |
-* `NetBoxModelFilterSetForm`
+| `NetBoxModelCSVForm`      | Bulk import objects from CSV data    |
+| `NetBoxModelBulkEditForm` | Edit multiple objects simultaneously |
+| `NetBoxModelFilterSetForm` | Filter objects within a list view   |
 
-<!-- TODO: Include forms reference -->
+### `NetBoxModelForm`
 
-In addition to the [form fields provided by Django](https://docs.djangoproject.com/en/stable/ref/forms/fields/), NetBox provides several field classes for use within forms to handle specific types of data. These can be imported from `utilities.forms.fields` and are documented below.
+This is the base form for creating and editing NetBox models. It extends Django's ModelForm to add support for tags and custom fields.
+
+| Attribute   | Description                                                 |
+|-------------|-------------------------------------------------------------|
+| `fieldsets` | A tuple of two-tuples defining the form's layout (optional) |
+
+**Example**
+
+```python
+from dcim.models import Site
+from netbox.forms import NetBoxModelForm
+from utilities.forms.fields import CommentField, DynamicModelChoiceField
+from .models import MyModel
+
+class MyModelForm(NetBoxModelForm):
+    site = DynamicModelChoiceField(
+        queryset=Site.objects.all()
+    )
+    comments = CommentField()
+    fieldsets = (
+        ('Model Stuff', ('name', 'status', 'site', 'tags')),
+        ('Tenancy', ('tenant_group', 'tenant')),
+    )
+
+    class Meta:
+        model = MyModel
+        fields = ('name', 'status', 'site', 'comments', 'tags')
+```
+
+!!! tip "Comment fields"
+    If your form has a `comments` field, there's no need to list it; this will always appear last on the page.
+
+### `NetBoxModelCSVForm`
+
+This form facilitates the bulk import of new objects from CSV data. As with model forms, you'll need to declare a `Meta` subclass specifying the associated `model` and `fields`. NetBox also provides several form fields suitable for import various types of CSV data, listed below.
+
+**Example**
+
+```python
+from dcim.models import Site
+from netbox.forms import NetBoxModelCSVForm
+from utilities.forms import CSVModelChoiceField
+from .models import MyModel
+
+class MyModelCSVForm(NetBoxModelCSVForm):
+    site = CSVModelChoiceField(
+        queryset=Site.objects.all(),
+        to_field_name='name',
+        help_text='Assigned site'
+    )
+
+    class Meta:
+        model = MyModel
+        fields = ('name', 'status', 'site', 'comments')
+```
+
+### `NetBoxModelBulkEditForm`
+
+This form facilitates editing multiple objects in bulk. Unlike a model form, this form does not have a child `Meta` class, and must explicitly define each field. All fields in a bulk edit form are generally declared with `required=False`.
+
+| Attribute         | Description                                                                                 |
+|-------------------|---------------------------------------------------------------------------------------------|
+| `model`           | The model of object being edited                                                            |
+| `fieldsets`       | A tuple of two-tuples defining the form's layout (optional)                                 |
+| `nullable_fields` | A tuple of fields which can be nullified (set to empty) using the bulk edit form (optional) |
+
+**Example**
+
+```python
+from django import forms
+from dcim.models import Site
+from netbox.forms import NetBoxModelCSVForm
+from utilities.forms import CommentField, DynamicModelChoiceField
+from .models import MyModel, MyModelStatusChoices
+
+class MyModelEditForm(NetBoxModelCSVForm):
+    name = forms.CharField(
+        required=False
+    )
+    status = forms.ChoiceField(
+        choices=MyModelStatusChoices,
+        required=False
+    )
+    site = DynamicModelChoiceField(
+        queryset=Site.objects.all(),
+        required=False
+    )
+    comments = CommentField()
+
+    model = MyModel
+    fieldsets = (
+        ('Model Stuff', ('name', 'status', 'site')),
+    )
+    nullable_fields = ('site', 'comments')
+```
+
+### `NetBoxModelFilterSetForm`
+
+This form class is used to render a form expressly for filtering a list of objects. Its fields should correspond to filters defined on the model's filter set.
+
+| Attribute         | Description                                                 |
+|-------------------|-------------------------------------------------------------|
+| `model`           | The model of object being edited                            |
+| `fieldsets`       | A tuple of two-tuples defining the form's layout (optional) |
+
+**Example**
+
+```python
+from dcim.models import Site
+from netbox.forms import NetBoxModelFilterSetForm
+from utilities.forms import DynamicModelMultipleChoiceField, MultipleChoiceField
+from .models import MyModel, MyModelStatusChoices
+
+class MyModelFilterForm(NetBoxModelFilterSetForm):
+    site_id = DynamicModelMultipleChoiceField(
+        queryset=Site.objects.all(),
+        required=False
+    )
+    status = MultipleChoiceField(
+        choices=MyModelStatusChoices,
+        required=False
+    )
+
+    model = MyModel
+```
 
 ## General Purpose Fields
 
+In addition to the [form fields provided by Django](https://docs.djangoproject.com/en/stable/ref/forms/fields/), NetBox provides several field classes for use within forms to handle specific types of data. These can be imported from `utilities.forms.fields` and are documented below.
+
 ::: utilities.forms.ColorField
     selection:
       members: false