Add custom docker registry authentication (#665)

* Add custom docker registry authentication

Uses DOCKER_USERNAME and DOCKER_PASSWORD as secrets provided into
the act cli.

Closes #527

Co-authored-by: Björn Brauer <zaubernerd@zaubernerd.de>

* Add test to check if pull authentication is filled in

* Update debug message to be more descriptive

Co-authored-by: Ryan (hackercat) <me@hackerc.at>

Co-authored-by: Björn Brauer <zaubernerd@zaubernerd.de>
Co-authored-by: Ryan (hackercat) <me@hackerc.at>

pkg/container/docker_run.go

@@ -37,6 +37,8 @@ import (
 // NewContainerInput the input for the New function
 type NewContainerInput struct {
 	Image       string
+	Username    string
+	Password    string
 	Entrypoint  []string
 	Cmd         []string
 	WorkingDir  string
@@ -126,6 +128,8 @@ func (cr *containerReference) Pull(forcePull bool) common.Executor {
 		Image:     cr.input.Image,
 		ForcePull: forcePull,
 		Platform:  cr.input.Platform,
+		Username:  cr.input.Username,
+		Password:  cr.input.Password,
 	})
 }
 func (cr *containerReference) Copy(destPath string, files ...*FileEntry) common.Executor {