Multiple Gateway backends Support

[Nabil-Salah]

Which package/s are you suggesting this feature for?

No response

Is your feature request related to a problem? Please describe

Currently zos support multiple gateway backend after this threefoldtech/zosbase#17

Describe the solution you'd like

Update gateway backends count support

[ramezsaeed]

Acceptance testing:

• deploy 2 VMs, use the 2 different IPs and had a server, and use these IPs for the domain, should balanced on the 2 VMs.

[ramezsaeed]

should remove the validation for gateway from the grid client to support multiple gateways not only one.

[samaradel]

update:
The feature implemented in the manage gateway dialog and still in testing on the domains page

[samaradel]

update:
Implement the multiple gateways as per the backend's new feature.