The EST RFC describes that EST is always served on a well known path:
`https://host:port/.well-known/est`
It also supports paths that contain a label, supporting multiple
authorities:
`https://host:port/.well-known/some-label/est`
Clients may be forming the URL to use based on just the base host
URL, and may or may not support using a label. We'll thus have to
keep that into account when serving EST.
The fact that the label comes after `.well-known` is not great, as
the label is then not namespaced. Anything else that we may want to
serve there could now be pointing to an EST provisioner too.
We currently don't know if EST clients support `/.well-known` to not
sit at the root, or whether they support suffix path parts and/or
query parameters. For now this is the conservative choice.
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