feat: add ability to recognize early access code in header (hacktoolk…

…it#444)

## Description
Django cannot receive cookie data from the react-native environment.
Instead of adding it as a query-parameter on every request, sending it
in the header was better.
This PR updates the `get_early_access_code` helper function to also get
the early access code from header `X-HTK-Early-Access-Code`

apps/prelaunch/utils.py

@@ -97,10 +97,12 @@ def is_prelaunch_exception_view(path):
 
 def get_early_access_code(request):
     key = 'early_access_code'
+    header = 'X-HTK-Early-Access-Code'
     early_access_code = (
         request.GET.get(key)
         or request.COOKIES.get(key)
         or request.session.get(key)
+        or request.headers.get(header)
     )
     return early_access_code