Users should never be in a position where they need to manually edit files managed by Dokku, and should be pushed to using the `domains` plugin where necessary.
Closes#3064
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While there are a number of enhancements we could do to make port handling more seamless, this is a first step towards documenting the various oddities around port management for Docker vs Buildpack deploys.
Refs #2903Closes#2970
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