Values:
* `legacy` (default): generate location blocks for ACME HTP Challenge
excepted when `HTTPS_METHOD=noredirect` or there is no certificate for
the domain
* `true`: generate location blocks for ACME HTP Challenge in all cases
* `false`: do not generate location blocks for ACME HTP Challenge
This feature is currently needed because acme-companion may generate
the HTTP Challenge configuration while it was done already by nginx-proxy
(see #2465#issuecomment-2136361373).
Also sometimes a hardcoded ACME challenge location is not wanted because
the challenge validation is not done with acme-companion / Let's Encrypt,
and with a challenge location setup differently.
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