Add a sandbox mode for experimentation
Add an optional sandbox mode in which users can browse and install themes and plugins to experiment with.
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Add some way for sandbox mode to be enabled that is not easy to do in ignorance. 
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Make WP_CONTENT_DIRwritable for the PHP-FPM user and disable the filter which intercepts user write-permissions checks.
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Trigger the entrypoint's static file gather function after (un)install.
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Add BDD tests for sandbox/regular mode installs (or attempts to install) 
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Document how to enable the mode and when to (not) enable it. 
Edited  by Dom Sekotill