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The ability to configure Arduino CLI via environment variables is only documented by a mention in the integration options article, which is not an obvious place to look for that information. Since this information didn't fit well in any of the existing pages, it makes sense to add a dedicated page, and add some documentation for the other two configuration methods as well. Although there is existing documentation for the other configuration methods elsewhere in the docs, it is missing some useful specifics, which wouldn't be appropriate to add there.