Issues #258 - Stubbed validateDockerImage

Was validating pipeline environment image as an AMI when it
is actually a docker image. The registry/image:tag regex
is fairly complicated and varies between v1 and v2
of the registries. For now just adding an empty method where
validation may occur later if we want.

common/types.go

@@ -174,7 +174,7 @@ type Pipeline struct {
 		Disabled     bool            `yaml:"disabled,omitempty"`
 		Type         EnvironmentType `yaml:"type,omitempty"`
 		ComputeType  ComputeType     `yaml:"computeType,omitempty"`
-		Image        string          `yaml:"image,omitempty" validate:"validateResourceID=ami"`
+		Image        string          `yaml:"image,omitempty" validate:"validateDockerImage"`
 		Bucket       string          `yaml:"bucket,omitempty"`
 		BuildTimeout string          `yaml:"timeout,omitempty" validate:"max=480"`
 	} `yaml:"build,omitempty"`
@@ -183,7 +183,7 @@ type Pipeline struct {
 		Environment string          `yaml:"environment,omitempty"`
 		Type        EnvironmentType `yaml:"type,omitempty"`
 		ComputeType ComputeType     `yaml:"computeType,omitempty"`
-		Image       string          `yaml:"image,omitempty" validate:"validateResourceID=ami"`
+		Image       string          `yaml:"image,omitempty" validate:"validateDockerImage"`
 		Roles       struct {
 			CodeBuild string `yaml:"codeBuild,omitempty" validate:"validateRoleARN"`
 			Mu        string `yaml:"mu,omitempty" validate:"validateRoleARN"`

common/validate.go

@@ -25,6 +25,7 @@ func validators() {
 	validator.SetValidationFunc("validateURL", validateURL)
 	validator.SetValidationFunc("validateInstanceType", validateInstanceType)
 	validator.SetValidationFunc("validateCIDR", validateCIDR)
+	validator.SetValidationFunc("validateDockerImage", validateDockerImage)
 }
 
 func validateResourceID(v interface{}, param string) error {
@@ -60,6 +61,11 @@ func validateCIDR(v interface{}, param string) error {
 	return regexpLength(reflect.ValueOf(v).String(), pattern, 18)
 }
 
+func validateDockerImage(v interface{}, param string) error {
+	// TODO: Validate Docker Image registry/image:tag
+	return nil
+}
+
 // validateRoleARN validates that the value is an valid role ARN
 func validateRoleARN(v interface{}, param string) error {
 	value := reflect.ValueOf(v).String()