Configure proxy timeouts and payload size

[filippomc]

Closes #701

Implemented solution: added values-based configuration for ingress and gatekeepers

How to test this PR: change values-template.yaml file proxy.timeout.send and check it is reflected in the ingress
spec and gatekeepers configmap.

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[zsinnema]

lgtm

[afonsobspinto]

Tested in ebrains and it worked 👍