Resolve "Use secrets from an .env file rather than from individual files"

Closes #804

See merge request openappstack/openappstack!416

Otherwise such errors like https://open.greenhost.net/openappstack/openappstack/-/jobs/89464
are not catched:

    $ sh ./install/install-openappstack.sh
    ✚ generating manifests
     manifests build completed
    ► installing components in flux-system namespace
    ✗ install failed: exec: "kubectl": executable file not found in $PATH
    ✚ generating GitRepository source
    ► applying GitRepository source
     GitRepository source created
    ◎ waiting for GitRepository source reconciliation
     GitRepository source reconciliation completed
     fetched revision: master/fe6c3302
    ✚ generating Kustomization
    ► applying Kustomization
     Kustomization created
    ◎ waiting for Kustomization reconciliation
     Kustomization openappstack is ready
     applied revision master/fe6c3302

Resolve "Update musl-dev, curl, curl-dev"

Closes #809 and #808

See merge request openappstack/openappstack!415

Fixes: #809

Fixes: #808

Try Flux 2

See merge request openappstack/openappstack!405

Remove prometheus_enable_ingress setting

See merge request openappstack/openappstack!410

Prometheus ingress is enabled by default now

Resolve "Add proper labels to eventrouter logs"

Closes #709

See merge request openappstack/openappstack!408