Add support for environment variable secrets

Env var secrets are env vars that are set inside the container but not
commited to and image. Also support reading from env var when creating a
secret.

Signed-off-by: Ashley Cui <acui@redhat.com>

libpod/options.go

@@ -1703,6 +1703,28 @@ func WithSecrets(secretNames []string) CtrCreateOption {
 	}
 }
 
+// WithSecrets adds environment variable secrets to the container
+func WithEnvSecrets(envSecrets map[string]string) CtrCreateOption {
+	return func(ctr *Container) error {
+		ctr.config.EnvSecrets = make(map[string]*secrets.Secret)
+		if ctr.valid {
+			return define.ErrCtrFinalized
+		}
+		manager, err := secrets.NewManager(ctr.runtime.GetSecretsStorageDir())
+		if err != nil {
+			return err
+		}
+		for target, src := range envSecrets {
+			secr, err := manager.Lookup(src)
+			if err != nil {
+				return err
+			}
+			ctr.config.EnvSecrets[target] = secr
+		}
+		return nil
+	}
+}
+
 // WithPidFile adds pidFile to the container
 func WithPidFile(pidFile string) CtrCreateOption {
 	return func(ctr *Container) error {