Proof of concept of the workflow instance context

Add support for workflow instance JSON context.
Add support for two step workflow transition.
Add support for dynamic form creation for transition execution.

Signed-off-by: Roberto Rosario <roberto.rosario@mayan-edms.com>

mayan/apps/document_states/forms.py

@@ -165,11 +165,11 @@ WorkflowTransitionTriggerEventRelationshipFormSet = formset_factory(
 )
 
 
-class WorkflowInstanceTransitionForm(forms.Form):
+class WorkflowInstanceTransitionSelectForm(forms.Form):
     def __init__(self, *args, **kwargs):
         user = kwargs.pop('user')
         workflow_instance = kwargs.pop('workflow_instance')
-        super(WorkflowInstanceTransitionForm, self).__init__(*args, **kwargs)
+        super(WorkflowInstanceTransitionSelectForm, self).__init__(*args, **kwargs)
         self.fields[
             'transition'
         ].queryset = workflow_instance.get_transition_choices(_user=user)
@@ -177,14 +177,6 @@ class WorkflowInstanceTransitionForm(forms.Form):
     transition = forms.ModelChoiceField(
         label=_('Transition'), queryset=WorkflowTransition.objects.none()
     )
-    comment = forms.CharField(
-        help_text=_('Optional comment to attach to the transition.'),
-        label=_('Comment'), required=False, widget=forms.widgets.Textarea(
-            attrs={
-                'rows': 3
-            }
-        )
-    )
 
 
 class WorkflowPreviewForm(forms.Form):