Add Persistent and Temporary mode for managing secrets

[nanderstabel]

Description

We use a SecretManager for managing secrets in both agent_issuance and agent_verification. Under the hood, the SecretManager uses a Stronghold file where the secrets are actually stored. We need to be able to properly support 3 scenario's:

• Temporary Mode: the UniCore consumer does not supply their own Stronghold file. On spin-up UniCore will generate a new Stronghold file that the SecretManager will utilize. The Stronghold file will be lost once the docker container is stopped.
• Persistent Mode with external Stronghold: the UniCore consumer supplies their own Stronghold file that the SecretManager will utilize.
• Persistent Mode without external Stronghold: the UniCore consumer does not supply their own Stronghold file. On first spin-up UniCore will generate a new Stronghold file which can be reused.

Motivation

Support different use cases:

• For simple testing
• For self management of secrets
• For dynamic secret management

Resources

n/a

To-do List

• Support Temporary Mode
• Support Persistent Mode (dynamic)
• Support Temporary Mode with external Stronghold (static)