story(config): implement source interface on manager

[Zaba505]

Description

As a user, I want the config.Manager to implement the config.Source interface because I may need/want to read config.Sources before passing them to config.Read.

The scenario where this really appears is reading config.Sources before then passing them to bedrock.Run. The problem here is that config.Source is not guaranteed to be repeatable. Thus, when bedrock.Run tries to read the already read config.Sources it fails often times because the underlying io.Readers are now empty.

Acceptance Criteria

• config.Manager should implement config.Source
• update config.Read in case of only one config.Source and it's already a config.Manager

Related Issues

No response