certificate files configuration should be centralized

[GuillaumeHold]

the certificates variables are defined at multiple places in collections :

• tdp-getting-started :

tdp-getting-started/inventory/group_vars/all.yml

Line 20 in 9a51db8

ca_file: "{{ certs_dir }}/tdp_ca.crt"

• tdp-collection-prerequisites :

https://github.com/TOSIT-IO/tdp-collection-prerequisites/blob/15113babf526ce794639bbf162bc2cfd1a711bce/roles/certificates/defaults/main.yml#L10

https://github.com/TOSIT-IO/tdp-collection-prerequisites/blob/15113babf526ce794639bbf162bc2cfd1a711bce/roles/ldap_kerberos/defaults/main.yml#L104

• tdp-collection-extras :

https://github.com/TOSIT-IO/tdp-collection-extras/blob/832e370998cdfdebd96db362bdc3e92c372894d6/tdp_vars_defaults/hue/hue.yml#L36

we should be able to centralize certificates configuration in tdp-cluster