Show the first line of the address from the to field.

Now persisting the address to the "to" field of the Notification, after the notification has been validated.
If the letter is pending validation, then "Checking..." will appear as the identifier for the letter.
If the letter has passed validation, then the first line of the address (now persisted in the "to" field) will be displayed, with the client reference underneath.
If the letter has failed validation the "Provided as PDF" will show be displayed, which is now the initial value of the "to" field.

app/main/views/uploads.py

@@ -1,5 +1,6 @@
 import base64
 import json
+import urllib
 import uuid
 from io import BytesIO
 
@@ -168,6 +169,25 @@ def _get_error_from_upload_form(form_errors):
     return error
 
 
+def format_recipient(address):
+    '''
+    To format the recipient we need to:
+        - decode, address is url encoded
+        - remove new line characters
+        - remove whitespace around the lines
+        - join the address lines, separated by a comma
+    '''
+    if not address:
+        return address
+    address = urllib.parse.unquote(address)
+    stripped_address_lines_no_trailing_commas = [
+        line.lstrip().rstrip(' ,')
+        for line in address.splitlines() if line
+    ]
+    one_line_address = ', '.join(stripped_address_lines_no_trailing_commas)
+    return one_line_address
+
+
 @main.route("/services/<uuid:service_id>/preview-letter/<uuid:file_id>")
 @user_has_permissions('send_messages')
 def uploaded_letter_preview(service_id, file_id):
@@ -179,7 +199,7 @@ def uploaded_letter_preview(service_id, file_id):
     status = metadata.get('status')
     error_shortcode = metadata.get('message')
     invalid_pages = metadata.get('invalid_pages')
-    recipient = metadata.get('recipient')
+    recipient = format_recipient(metadata.get('recipient'))
 
     if invalid_pages:
         invalid_pages = json.loads(invalid_pages)
@@ -246,11 +266,12 @@ def send_uploaded_letter(service_id):
     postage = form.postage.data
     metadata = get_letter_metadata(service_id, file_id)
     filename = metadata.get('filename')
+    recipient_address = metadata.get('recipient')
 
     if metadata.get('status') != 'valid':
         abort(403)
 
-    notification_api_client.send_precompiled_letter(service_id, filename, file_id, postage)
+    notification_api_client.send_precompiled_letter(service_id, filename, file_id, postage, recipient_address)
 
     return redirect(url_for(
         '.view_notification',