Clairfy required base64 encoding of file content references

[neilmock]

The docs are misleading on what values need to be base64 encoded, particularly w/r/t secret values that hydrate files, so hopefully this clarifies.

[andie787]

@neilmock Would you mind clarifying what's misleading? I'm not sure of the difference between

• The contents of ... secret_name must be base64 encoded. and your suggestion
• "...the value of the secret must be base64 encoded."

The content of secret_name is the value of the secret right?