PLT-3647 Email Batching (#3718)

* PLT-3647 Added config settings for email batching

* PLT-3647 Refactored generation of email notification

* PLT-3647 Added serverside code for email batching

* PLT-3647 Updated settings UI to enable email batching

* PLT-3647 Removed debug code

* PLT-3647 Fixed 0-padding of minutes in batched notification

* PLT-3647 Updated clientside UI for when email batching is disabled

* Go fmt

* PLT-3647 Changed email batching to be disabled by default

* Updated batched email message

* Added email batching toggle to system console

* Changed Email Notifications > Immediate setting to a 30 second batch interval

* Go fmt

* Fixed link to Mattermost icon in batched email notification

* Updated users to use 30 second email batching by default

* Fully disabled email batching when clustering is enabled

* Fixed email batching setting in the system console

* Fixed casing of 'Send Email notifications' -> 'Send email notifications'

* Updating UI Improvements for email batching (#3736)

* Updated text for notification settings and SiteURL.

* Prevented enabling email batching when SiteURL isn't set in the system console

* Re-added a couple debug messages

* Added warning text when clustering is enabled

templates/post_batched_body.html

@@ -0,0 +1,43 @@
+{{define "post_batched_body"}}
+
+<table align="center" border="0" cellpadding="0" cellspacing="0" width="100%" style="margin-top: 20px; line-height: 1.7; color: #555;">
+    <tr>
+        <td>
+            <table align="center" border="0" cellpadding="0" cellspacing="0" width="100%" style="max-width: 660px; font-family: Helvetica, Arial, sans-serif; font-size: 14px; background: #FFF;">
+                <tr>
+                    <td style="border: 1px solid #ddd;">
+                        <table align="center" border="0" cellpadding="0" cellspacing="0" width="100%" style="border-collapse: collapse;">
+                            <tr>
+                                <td style="padding: 20px 20px 10px; text-align:left;">
+                                    <img src="{{.Props.SiteURL}}/static/images/logo-email.png" width="130px" style="opacity: 0.5" alt="">
+                                </td>
+                            </tr>
+                            <tr>
+                                <td>
+                                    <table border="0" cellpadding="0" cellspacing="0" style="padding: 20px 50px 0; text-align: center; width: 100%;">
+                                        <tr>
+                                            <td style="border-bottom: 1px solid #ddd; margin: 10px 0 20px;">
+                                                <p style="font-weight: normal; text-align: left;">
+                                                    {{.Props.BodyText}}
+                                                </p>
+                                                {{.Props.Posts}}
+                                            </td>
+                                        </tr>
+                                        <tr>
+                                            {{template "email_info" . }}
+                                        </tr>
+                                    </table>
+                                </td>
+                            </tr>
+                            <tr>
+                                {{template "email_footer" . }}
+                            </tr>
+                        </table>
+                    </td>
+                </tr>
+            </table>
+        </td>
+    </tr>
+</table>
+
+{{end}}

templates/post_batched_post.html

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+{{define "post_batched_post"}}
+
+<table style="border-top: 1px solid #ddd; padding: 20px 0; width: 100%">
+    <tr>
+        <td style="text-align: left">
+            <span style="font-size: 16px; font-weight: bold; color: #555;" >
+                {{.Props.ChannelName}}
+            </span>
+            <br/>
+            <span style="font-weight: bold">
+                @{{.Props.SenderName}}
+            </span>
+            <span style="color: #AAA; font-size: 12px; margin-left: 2px;">
+                {{.Props.Date}}
+            </span>
+        </td>
+        <td valign="top" style="width: 120px; padding-top: 3px;">
+            <a href="{{.Props.PostLink}}" style="background: #2389D7; display: inline-block; border-radius: 2px; color: #fff; padding: 4px 0; width: 120px; text-decoration: none;">
+                {{.Props.Button}}
+            </a>
+        </td>
+    </tr>
+    <tr>
+        <td colspan=2>
+            <pre style="text-align:left; font-family: 'Lato', sans-serif; margin: 0px; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word; line-height: 20px;">{{.Props.PostMessage}}</pre>
+        </td>
+    </tr>
+</table>
+
+{{end}}