Task: Include TUF configuration for Archivista

[kairoaraujo]

The implementation enables the user to configure Archivista to integrate with RSTUF.

Using the same configuration process to set up the ARCHIVISTA_STORAGE_BACKEND, the user can set up ARCHIVISTA_RSTUF_BACKEND and define the URL for accessing the RSTUF API.

This configuration enables Archivista to use TUF/RSTUF and uses TUF tufstorage while storing Attestations or Policy.

Requires:

• Task: Implement the tufstorage in internal #236

Parent feature

• Feature|Experimental: Add support to add Policies to TUF #159