add ability to include custom parameters on respondent gateawy url creation

Author: dy-waltergrantward

README.md

@@ -63,10 +63,32 @@ signed_link = gateway.create_respondent_url(url,
                                             'male',
                                             '90210',
                                             'very-unique-respondent-id',
+                                            
                                             ttl=60)
 # https://respondent.fake.rex.dynata.com/start?ctx=XXXX&language=en&birth_date=1990-01-01&gender=male&postal_code=90210&respondent_id=very-unique-respondent-id&access_key=rex_access_key&expiration=2021-11-29T15:35:12.993Z&signature=4353e8c4ca8f8fb75530214ac78139b55ca3f090438c639476b8584afe1396e6
 ```
 
+### Add additional query parameters to a link that will be present on return from survey
+```
+url = 'https://respondent.fake.rex.dynata.com/start?ctx=XXXX&language=en'
+
+custom_params = {
+    'custom_parameter': 'custom_value',
+    'another_custom_parameter': 'another_custom_value'
+}
+
+signed_link = gateway.create_respondent_url(url,
+                                            '1990-01-01',
+                                            'male',
+                                            '90210',
+                                            'very-unique-respondent-id',
+                                            additional_params=custom_params,
+                                            ttl=60)
+
+# https://respondent.fake.rex.dynata.com/start?ctx=XXXX&language=en&custom_parameter=custom_value&another_custom_parameter=another_custom_value&birth_date=1990-01-01&gender=male&postal_code=90210&respondent_id=very-unique-respondent-id&access_key=rex_access_key&expiration=2021-12-02T13:48:55.759Z&signature=cf443326b73fb8af14c590e18d79a970fc3f73327c2d140c324ee1ce3020d064
+```
+
+
 ### Sign an inbound /start link with your credentials
 ```
 url = 'https://respondent.fake.rex.dynata.com/start?ctx=XXXX&language=en'

dynata_rex/respondent_gateway.py

@@ -56,6 +56,7 @@ def create_respondent_url(self,
                               gender: str,
                               postal_code: str,
                               respondent_id: str,
+                              additional_params: dict = None,
                               ttl: Union[int, None] = None,
                               url_quoting: bool = False) -> str:
         """
@@ -67,9 +68,16 @@ def create_respondent_url(self,
         @gender: 'male' / 'female'
         @postal: postal code as string
         @respondent_id : unique identifier for the respondent
+
+        @additional_params: additional parameters that will be included
+            on the return back from the survey
+        @ttl: time to live for signature in seconds
+        @url_quoting: whether to URL quote the returned URL
         """
         parsed = urlparse(url)
         base_params = dict(parse_qsl(parsed.query))
+        if additional_params:
+            base_params = dict(base_params, **additional_params)
         required_params = {
             'birth_date': birth_date,
             'gender': gender,