* validate required storage props (#85)
Centralizes validation of required storage config properties within
the storage package. Requiremens are checked eagerly at
configuration creation, and lazily at config retrieval.
Additionally, updates /pkg/storage tests to use suites
and assert funcs.
* add validation failure tests to storage
* add common config and encryption passwd
Adds a provider-independent configuration handler, and the
the encryption password config property. The password is used
to encrypt and decrypt the kopia repository properties file.
* fix corso_password in ci.yml
* actually use the corso password in testing
* replace passwd in ci.yml with a secret
* ci.yml secret typo fix
A small collection of changes and code cleanup to successfully run
'corso repo init s3' manually. Adds a default s3 url (might want
this configurable for local testing) and aws session token support.
* introduces storage pkg (#25)
Adds a new package /pkg/storage. Storage is used to
communicate storage provider information throughout the corso
app. In particular, it allows per-provider data to cross interface
boundaries without slicing their details.
* use consts for s3 config keys
