MDL-57122 boost: Add context docs to login template

theme/boost/templates/core/login.mustache

@@ -18,6 +18,79 @@
     @template core/login
 
     Moodle template for the login page.
+
+    Context variables required for this template:
+    * autofocusform: Auto focus on form ?,
+    * canloginasguest - Is guest login allowed?,
+    * canloginbyemail - Is login by email allowed?,
+    * cansignup - Signup allowed?,
+    * cookieshelpicon - cookies help icon details
+    * error - Any errors in the form?,
+    * forgotpasswordurl - Forgot password url,
+    * hasidentityproviders - Flag, set to true to hide identity providers,
+    * hasinstructions - Flag, set to true to show instructions,
+    * identityproviders - List of identiy providers,
+    * instructions - Instructions,
+    * instructionsformat - Format of instructions,
+    * loginurl - Login url,
+    * rememberusername - Remeber username?,
+    * passwordautocomplete - Allow password autocomplete?,
+    * signupurl - Signup url,
+    * cookieshelpiconformatted - Formatted html of cookies help icon,
+    * errorformatted - Formatted error,
+    * logourl - Flag, logo url,
+    * sitename - Name of site.
+
+    Example context (json):
+    {
+        "autofocusform": false,
+        "canloginasguest": "1",
+        "canloginbyemail": false,
+        "cansignup": true,
+        "cookieshelpicon": {
+            "heading": "Cookies must be enabled in your browser",
+            "text": "<div class=\"no-overflow\">Two cookies are used on this site. Both died..</div>",
+            "icon": {
+                "attributes": [
+                    {
+                        "name": "class",
+                        "value": "iconhelp"
+                    },
+                    {
+                        "name": "alt",
+                        "value": "Help with Cookies must be enabled in your browser"
+                    },
+                    {
+                        "name": "title",
+                        "value": "Help with Cookies must be enabled in your browser"
+                    },
+                    {
+                        "name": "src",
+                        "value": "http://localhost/stable_master/theme/image.php?theme=boost&component=core&image=help"
+                    }
+                ]
+            },
+            "linktext": null,
+            "title": "Help with Cookies must be enabled in your browser",
+            "url": "http://localhost/stable_master/help.php?component=core&identifier=cookiesenabled&lang=en",
+            "ltr": true
+        },
+        "error": "",
+        "forgotpasswordurl": "http://localhost/stable_master/login/forgot_password.php",
+        "hasidentityproviders": false,
+        "hasinstructions": true,
+        "identityproviders": [],
+        "instructions": "For full access to this site, you first need to create an account.",
+        "instructionsformat": "1",
+        "loginurl": "http://localhost/stable_master/login/index.php",
+        "rememberusername": true,
+        "passwordautocomplete": false,
+        "signupurl": "http://localhost/stable_master/login/signup.php",
+        "cookieshelpiconformatted": "",
+        "errorformatted": "",
+        "logourl": false,
+        "sitename": "Beer & Chips"
+    }
 }}
 
 <div class="m-y-3 hidden-sm-down"></div>