Fix display of registration on dashboard

Ensure the registration information is displayed to any user
who can use a component of the section, regardless of if
there are available categories for them to purchase from.

pinaxcon/templates/dashboard.html

@@ -16,8 +16,8 @@
 
 {% block content %}
 
-{% available_categories as categories %}
+{% registration_available as show_registration %}
-{% if categories %}
+{% if show_registration %}
   {% include "symposion/dashboard/_categories.html" %}
 {% endif %}
 

vendor/registrasion/registrasion/templatetags/registrasion_tags.py

@@ -21,6 +21,25 @@ def user_for_context(context):
         return context.request.user
 
 
+@register.simple_tag(takes_context=True)
+def registration_available(context):
+    ''' Checks if registration is available for the user. '''
+    user = user_for_context(context)
+    if user.is_staff:
+        # Staff can always see registration - not necessarily all parts.
+        return True
+
+    if user.attendee.completed_registration:
+        # Always show to someone who has completed registration already.
+        return True
+
+    if available_categories(context):
+        # Not yet registered, but has categories available to purchase from.
+        return True
+
+    return False
+
+
 @register.simple_tag(takes_context=True)
 def available_categories(context):
     ''' Gets all of the currently available products.
@@ -49,6 +68,7 @@ def missing_categories(context):
 
     return sorted(set(i for i in missing), key=attrgetter("order"))
 
+
 @register.simple_tag(takes_context=True)
 def available_credit(context):
     ''' Calculates the sum of unclaimed credit from this user's credit notes.