Add missing CMS config (just in case)

I don't think this affects the CMS behaviour, but SESSION_COOKIE_DOMAIN
is used by the CMS, so rather be safe than sorry.

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## Latest
+
+- [Improvement] Support CMS login when the CMS is not a subdomain of the LMS
+
 ## 3.3.0 (2019-03-22)
 
 - [Feature] Upgrade from Hawthorn to Ironwood

tutor/config.py

@@ -164,6 +164,9 @@ def load_defaults(config):
         if k not in config:
             config[k] = v
 
+    # Add extra configuration parameters that need to be computed separately
+    config["lms_cms_common_domain"] = utils.common_domain(config["LMS_HOST"], config["CMS_HOST"])
+
 def ask(question, key, config):
     default = env.render_str(config, config[key])
     config[key] = click.prompt(

tutor/templates/apps/openedx/config/cms.env.json

@@ -33,6 +33,7 @@
   "EMAIL_PORT": {{ SMTP_PORT }},
   "HTTPS": "{{ "on" if ACTIVATE_HTTPS else "off" }}",
   "LANGUAGE_CODE": "{{ LANGUAGE_CODE }}",
+  "SESSION_COOKIE_DOMAIN": ".{{ lms_cms_common_domain }}",
   "CACHES": {
     "default": {
       "KEY_PREFIX": "default",

tutor/templates/apps/openedx/config/lms.env.json

@@ -44,7 +44,7 @@
   {% endif %}
   "LANGUAGE_CODE": "{{ LANGUAGE_CODE }}",
   "LOGIN_REDIRECT_WHITELIST": ["{{ CMS_HOST }}", "studio.localhost"],
-  "SESSION_COOKIE_DOMAIN": ".{{ LMS_HOST }}",
+  "SESSION_COOKIE_DOMAIN": ".{{ lms_cms_common_domain }}",
   "CACHES": {
     "default": {
       "KEY_PREFIX": "default",

tutor/utils.py

@@ -21,6 +21,22 @@ def parse_yaml_value(v):
         v = (v == "true")
     return v
 
+def common_domain(d1, d2):
+    """
+    Return the common domain between two domain names.
+
+    Ex: "sub1.domain.com" and "sub2.domain.com" -> "domain.com"
+    """
+    components1 = d1.split(".")[::-1]
+    components2 = d2.split(".")[::-1]
+    common = []
+    for c in range(0, min(len(components1), len(components2))):
+        if components1[c] == components2[c]:
+            common.append(components1[c])
+        else:
+            break
+    return ".".join(common[::-1])
+
 def docker_run(*command):
     return docker("run", "--rm", "-it", *command)