Start allowing any three lines in addresses

This is part of moving away from `postcode` and towards `address line 7`

We think it will be easier for people to map their existing data to our
API if we let them fill in any 3 lines, instead of requiring at least
1, 2, and postcode specifically.

app/schema_validation/definitions.py

@@ -27,29 +27,6 @@ personalisation = {
 }
 
 
-letter_personalisation = dict(
-    personalisation,
-    properties={
-        "address_line_1": {
-            "type": "string",
-            "minLength": 1,
-            "validationMessage": "address_line_1 is required"
-        },
-        "address_line_2": {
-            "type": "string",
-            "minLength": 1,
-            "validationMessage": "address_line_2 is required"
-        },
-        "postcode": {
-            "type": "string",
-            "minLength": 1,
-            "validationMessage": "postcode is required"
-        },
-    },
-    required=["address_line_1", "address_line_2", "postcode"],
-)
-
-
 https_url = {
     "type": "string",
     "format": "uri",

app/v2/notifications/notification_schemas.py

@@ -4,7 +4,7 @@ from app.models import (
     NOTIFICATION_STATUS_LETTER_RECEIVED,
     TEMPLATE_TYPES
 )
-from app.schema_validation.definitions import (uuid, personalisation, letter_personalisation)
+from app.schema_validation.definitions import (uuid, personalisation)
 
 
 template = {
@@ -226,7 +226,7 @@ post_letter_request = {
     "properties": {
         "reference": {"type": "string"},
         "template_id": uuid,
-        "personalisation": letter_personalisation
+        "personalisation": personalisation
     },
     "required": ["template_id", "personalisation"],
     "additionalProperties": False

app/v2/notifications/post_notifications.py

@@ -348,8 +348,22 @@ def process_letter_notification(*, letter_data, api_key, template, reply_to_text
                                                         template=template,
                                                         reply_to_text=reply_to_text)
 
-    if not PostalAddress.from_personalisation(letter_data['personalisation']).postcode:
-        raise ValidationError(message='Must be a real UK postcode')
+    address = PostalAddress.from_personalisation(letter_data['personalisation'])
+
+    if not address.has_enough_lines:
+        raise ValidationError(
+            message=f'Address must be at least {PostalAddress.MIN_LINES} lines'
+        )
+
+    if address.has_too_many_lines:
+        raise ValidationError(
+            message=f'Address must be no more than {PostalAddress.MAX_LINES} lines'
+        )
+
+    if not address.postcode:
+        raise ValidationError(
+            message='Must be a real UK postcode'
+        )
 
     test_key = api_key.key_type == KEY_TYPE_TEST