Add support for knox topology customization

[GuillaumeHold]

Which issue(s) this PR fixes

Fixes #804

Additional comments

Agreements

• I hereby declare this contribution to be licensed under the Apache License Version 2.0, January 2004.
• I hereby agree to grant TOSIT a copyright license to use my contributions.

[rpignolet]

We need to understand your use case because tdp_vars already combine dict when using tdp init --overrides ... for example.

[GuillaumeHold]

This allow to change the content of a provider, authentication for example. Currently, by changing the gateway_topology variable, the providers name will change, but the parameters will be appended to the default ones.