The force upgrade field is set to True on most HelmReleases

While debugging the issue #1360 (closed), I noticed that most helmreleases have the following spec:

upgrade:
   force: true

Although this is not defined in the units or in unit_helmrelease_spec_default.

with @tmmorin and @feleouet , we suspect it might be related to the merge-append (https://gitlab.com/sylva-projects/sylva-core/-/blob/main/charts/sylva-units/templates/_helpers.tpl?ref_type=heads#L448) used via

{{- $_ := tuple $helmrelease_spec $envAll.Values.unit_helmrelease_spec_default $unit_def.helmrelease_spec | include "merge-append" -}}

(The fact that this field is positioned to true could cause the errors on Thanos and Harbor seen in #1360 (closed). The following comments lead me to believe that: https://github.com/helm/helm/issues/6378#issuecomment-557746499 and https://github.com/helm/helm/issues/6378#issuecomment-735287919)