Add storage and bandwidth usage to instance dashboard
### Is your feature request related to a problem? Please describe The instance dashboard should display some analytics. ### Describe the solution you'd like The instance dashboard should display: - Number of uploaded bytes per month as a graph ``` SELECT sum(file_size), DATE_FORMAT(`updated_at`,'%Y-%m') AS month FROM `cp_media` GROUP BY month ORDER BY month; ``` - Number of total uploaded bytes ``` SELECT sum(file_size) FROM `cp_media`; ``` - Number of downloaded bytes per months as a graph ``` SELECT sum(`bandwidth`), DATE_FORMAT(`updated_at`,'%Y-%m') AS month FROM `cp_analytics_podcasts` GROUP BY month ORDER BY month; ```
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