Add the provide SSH public key to the core user's list of authorized keys.

WriteEnvFile updates an existing env `KEY=value` formated file with new values provided in EnvFile.Vars; File.Content is ignored.

WriteFile writes given endecoded file to the filesystem.

Etcd is a top-level structure which embeds its underlying configuration, config.Etcd, and provides the system-specific Unit().

Etcd2 is a top-level structure which embeds its underlying configuration, config.Etcd2, and provides the system-specific Unit().

File is a top-level structure which embeds its underlying configuration, config.File, and provides the system-specific Permissions().

flannel is a top-level structure which embeds its underlying configuration, config.Flannel, and provides the system-specific Unit().

Fleet is a top-level structure which embeds its underlying configuration, config.Fleet, and provides the system-specific Unit().

Locksmith is a top-level structure which embeds its underlying configuration, config.Locksmith, and provides the system-specific Unit().

OEM is a top-level structure which embeds its underlying configuration, config.OEM, and provides the system-specific File().

Unit is a top-level structure which embeds its underlying configuration, config.Unit, and provides the system-specific Destination(), Type(), and Group().

Update is a top-level structure which contains its underlying configuration, config.Update, a function for reading the configuration (the default implementation reading from the filesystem), and provides the system-specific File() and Unit().