Enable the use of a custom name for frontend-image

[hgo-ds]

As a trace-x frontend operator,
I want to be able to deploy and run a frontend image which might have a different name then frontend.
So that the name of the image and therefore the image itself can be freely chosen.

Hints / Details

• For that, introduce a placeholder for the image name-suffix which can be overwritten by others, prefilled with the value frontend.

  This means that this hard-coded image construct is fully customizable.
  image: "{{ .Values.image.repository }}-frontend:{{ .Values.image.tag | default .Chart.AppVersion }}",

  see https://github.com/catenax-ng/tx-traceability-foss/blob/main/charts/traceability-foss/charts/frontend/templates/deployment.yaml#L62

Acceptance Criteria

• The name of the image can be customized in the provided values file.

Out of Scope

• ./.