ECOM-1060: Logistration third-party auth improvements

When the user returns to the registration page with a current
third party auth provider, hide the third party auth buttons
are hidden, including the
"or create a new one here" text that does not make sense
when the buttons are hidden.

lms/static/sass/views/_login-register.scss

@@ -84,7 +84,7 @@ $sm-btn-linkedin: #0077b5;
     form {
         border: 1px solid $gray-l4;
         border-radius: 5px;
-        padding: 0 25px;
+        padding: 0px 25px 20px 25px;
     }
 
     .section-title {
@@ -155,7 +155,7 @@ $sm-btn-linkedin: #0077b5;
         display: block;
         font-weight: normal;
         color: $gray;
-        margin: 10px;
+        margin: 10px 10px 0px 10px;
         color: $m-gray-l1;
         text-align: center;
     }

lms/templates/student_account/login.underscore

@@ -32,6 +32,7 @@
 
     <button type="submit" class="action action-primary action-update js-login login-button"><%- gettext("Sign in") %></button>
 
+    <% if ( context.providers.length > 0 && !context.currentProvider ) { %>
     <div class="login-providers">
         <div class="section-title lines">
             <h2>
@@ -48,6 +49,7 @@
             <% }
         }); %>
     </div>
+    <% } %>
 </form>
 
 <div class="toggle-form">

lms/templates/student_account/register.underscore

@@ -11,7 +11,7 @@
                 <%- _.sprintf( gettext("We just need a little more information before you start learning with %(platformName)s."), context ) %>
             </p>
         </div>
-    <% } else {  %>
+    <% } else if ( context.providers.length > 0 ) {  %>
         <div class="login-providers">
             <div class="section-title lines">
                 <h2>
@@ -28,14 +28,19 @@
             <%  }
             }); %>
         </div>
+        <div class="section-title lines">
+            <h2>
+                <span class="text"><%- gettext("or create a new one here") %></span>
+            </h2>
+        </div>
+    <% } else { %>
+        <div class="section-title lines">
+            <h2>
+                <span class="text"><%- gettext("Create a new account") %></span>
+            </h2>
+        </div>
     <% } %>
 
-    <div class="section-title lines">
-        <h2>
-            <span class="text"><%- gettext("or create a new one here") %></span>
-        </h2>
-    </div>
-
     <%= context.fields %>
 
     <button type="submit" class="action action-primary action-update js-register register-button"><%- gettext("Create your account") %></button>