This change allows using the passphrase secrets manager when creating
a stack managed by the Pulumi service. `pulumi stack init`, `pulumi
new` and `pulumi up` all learned a new optional argument
`--secrets-provider` which can be set to "passphrase" to force the
passphrase based secrets provider to be used. When unset the default
secrets provider is used based on the backend (for local stacks this
is passphrase, for remote stacks, it is the key managed by the pulumi
service).
As part of this change, we also initialize the secrets manager when a
stack is created, instead of waiting for the first time a secret
config value is stored. We do this so that if an update is run using
`pulumi.secret` before any secret configuration values are used, we
already have the correct encryption method selected for a stack.
We move the implementations of our secrets managers in to
`pkg/secrets` (which is where the base64 one lives) and wire their use
up during deserialization.
It's a little unfortunate that for the passphrase based secrets
manager, we have to require `PULUMI_CONFIG_PASSPHRASE` when
constructing it from state, but we can make more progress with the
changes as they are now, and I think we can come up with some ways to
mitigate this problem a bit (at least make it only a problem for cases
where you are trying to take a stack reference to another stack that
is managed with local encryption).
When constructing a Deployment (which is a plaintext representation of
a Snapshot), ensure that we encrypt secret values. To do so, we
introduce a new type `secrets.Manager` which is able to encrypt and
decrypt values. In addition, it is able to reflect information about
itself that can be stored in the deployment such that we can
deserialize the deployment into a snapshot (decrypting the values in
the process) without external knowledge about how it was encrypted.
The ability to do this is import for allowing stack references to
work, since two stacks may not use the same manager (or they will use
the same type of manager, but have different state).
The state value is stored in plaintext in the deployment, so it **must
not** contain sensitive data.
A sample manager, which just base64 encodes and decodes strings is
provided, as it useful for testing. We will allow it to be varried
soon.
