[ui feature] customize web console path

[jozef-slezak]

Is your feature request related to a problem? Please describe. Please, enable web console context path customization.

Describe the solution you'd like Same solution as https://github.com/hashicorp/consul/issues/1930

Describe alternatives you've considered A clear and concise description of any alternative solutions or features you've considered.

Explain any additional use-cases We need to proxy nomad, consul, vault consoles on-premise without subdomains

[schmichael]

hashicorp/nomad#6413 contains some more details around how the shared /v1/ API prefix complicates things as well and should be addressed at the same time as /ui/

[awarner-greshamtech]

If I could vote for this issue, I would. We are fleshing out our use of the HashiCorp stack and would really like to proxy all three UIs.