title: Django admin - how can I use save_related() to parse data from inline forms?
body: <p>I need to intercept when the user saves related (inline) data in django admin to call an external API.
  I have the following models: </p>
  
  <pre><code>class Hostel(models.Model):
      name = models.CharField(max_length=50)
      descr = models.CharField(max_length=200)
      ....
  
  class User(models.Model):
      name = models.CharField(max_length=50, blank=False)
      nick = models.CharField(max_length=20, blank=False)
      password = models.CharField(max_length=20, blank=False)
  
  class HostelGuest(models.Model):
      hostel = models.ForeignKey(Hostel)
      guest = models.ForeignKey(User)
      entry_date = models.DateTimeField(null=True,blank=True)
  
  class HostelEntryPoint(models.Model):
      hostel = models.ForeignKey(Hostel)  
      getting_here = models.CharField(max_length=300, blank=False)
      distance = models.CharField(max_length = 30, blank = True)
  </code></pre>
  
  <p>In admin.py I have in the same page Hostel as parent and HostelGuest and EntryPoint as children. Whenever some data in HostelGuest changes, I need to find out if it's add/delete/update and call an external API. I thought of using save_related() but I'm unable to parse the data received and figure out the action taken. This is as far as I got, any help will be much appreciated!</p>
  
  <pre><code>class HostelEntryPointInline(admin.TabularInline):
      model = HostelEntryPoint
      extra = 3
  
  class HostelGuestInline(admin.TabularInline):
      model=HostelGuest
      extra=4
  
  class HostelAdmin(admin.ModelAdmin):
      inlines = [HostelGuestInline, HostelEntryPointInline]
  
      def save_related(self, request, form, formsets, change):
          super(HostelAdmin, self).save_related(request, form, formsets, change)
          logger = logging.getLogger(__name__)
          obj = form.instance
          obj.save()
          for formset in formsets:
              for f in formset:
                  logger.error('form name:' + f.__class__.__name__)
                  logger.error('form:' + f.cleaned_data['guest'])
  
  admin.site.register(Hostel,HostelAdmin)
  </code></pre>