Enhance docs for email reporting (#8486)

* extend documentation about setting up email reporting

* mention EMAIL_REPORTS_USER

docs/installation.rst

@@ -963,24 +963,60 @@ Email Reports
 -------------
 Email reports allow users to schedule email reports for
 
-* slice and dashboard visualization (Attachment or inline)
-* slice data (CSV attachment on inline table)
+* chart and dashboard visualization (Attachment or inline)
+* chart data (CSV attachment on inline table)
+
+**Setup**
+
+Make sure you enable email reports in your configuration file
+
+.. code-block:: python
+
+    ENABLE_SCHEDULED_EMAIL_REPORTS = True
+
+Now you will find two new items in the navigation bar that allow you to schedule email
+reports
+
+* Manage -> Dashboard Emails
+* Manage -> Chart Email Schedules
 
 Schedules are defined in crontab format and each schedule
 can have a list of recipients (all of them can receive a single mail,
 or separate mails). For audit purposes, all outgoing mails can have a
 mandatory bcc.
 
-**Requirements**
+In order get picked up you need to configure a celery worker and a celery beat
+(see section above "Celery Tasks"). Your celery configuration also
+needs an entry ``email_reports.schedule_hourly`` for ``CELERYBEAT_SCHEDULE``.
 
-* A selenium compatible driver & headless browser
+To send emails you need to configure SMTP settings in your configuration file. e.g.
+
+.. code-block:: python
+
+    EMAIL_NOTIFICATIONS = True
+
+    SMTP_HOST = "email-smtp.eu-west-1.amazonaws.com"
+    SMTP_STARTTLS = True
+    SMTP_SSL = False
+    SMTP_USER = "smtp_username"
+    SMTP_PORT = 25
+    SMTP_PASSWORD = os.environ.get("SMTP_PASSWORD")
+    SMTP_MAIL_FROM = "insights@komoot.com"
+
+
+To render dashboards you need to install a local browser on your superset instance
 
   * `geckodriver <https://github.com/mozilla/geckodriver>`_ and Firefox is preferred
   * `chromedriver <http://chromedriver.chromium.org/>`_ is a good option too
-* Run `celery worker` and `celery beat` as follows ::
 
-    celery worker --app=superset.tasks.celery_app:app --pool=prefork -Ofair -c 4
-    celery beat --app=superset.tasks.celery_app:app
+You need to adjust the ``EMAIL_REPORTS_WEBDRIVER`` accordingly in your configuration.
+
+You also need to specify on behalf of which username to render the dashboards. In general
+dashboards and charts are not accessible to unauthorized requests, that is why the
+worker needs to take over credentials of an existing user to take a snapshot. ::
+
+    EMAIL_REPORTS_USER = 'username_with_permission_to_access_dashboards'
+
 
 **Important notes**
 
@@ -995,6 +1031,10 @@ mandatory bcc.
 * It is recommended to run separate workers for ``sql_lab`` and
   ``email_reports`` tasks. Can be done by using ``queue`` field in ``CELERY_ANNOTATIONS``
 
+* Adjust ``WEBDRIVER_BASEURL`` in your config if celery workers can't access superset via its
+  default value ``http://0.0.0.0:8080/`` (notice the port number 8080, many other setups use
+  port 8088).
+
 SQL Lab
 -------
 SQL Lab is a powerful SQL IDE that works with all SQLAlchemy compatible