Install REANA in the cern-vre cluster via tf helm provider

[goseind]

### Tasks
- [x] Lable nodes for HA installation
- [x] Configure values to use the correct storage
- [ ] Configure HPC backend
- [x] Configure domain and ingress for access
- [x] Test workflow run
- [ ] https://github.com/vre-hub/reana-cnaf-demo/issues/1
- [x] Configure IAM ESCAPE auth with new REANA release

[goseind]

REANA is installed with the values added in PR #35 and accessible under: https://188.185.29.170:30443/signin Nodes were labeled for HA as described here: https://docs.reana.io/administration/deployment/deploying-at-scale/#high-availability

Reana uses a thorough terraform created share, check the details via openstack share show cvre-reana and get the access id via openstack share access list cvre-reana.

The configuration is still pending, so it won't work yet.

Problems/open topics:

• Installation was done manually (helm install --devel reana-cvre reanahub/reana --wait --version 0.9.0 --values reana/values.yaml -n reana), due to the following unresolved error thrown by terraform: Error: could not download chart: Chart.yaml file is missing
• Create and connect postgres db
• exposing the service via LBaaS to the outside?

[egazzarr]

Reana cluster is accessible on: https://reana-vre.cern.ch/signin with IAM log in. The only thing still needed to do is the HPC connection.