rpk: Add config tests for NamedAuthNSocketAddress

Signed-off-by: Ben Pope <ben@redpanda.com>

src/go/rpk/pkg/config/config_test.go

@@ -47,6 +47,7 @@ func getValidConfig() *Config {
 }
 
 func TestSet(t *testing.T) {
+	authNSasl := "sasl"
 	tests := []struct {
 		name      string
 		key       string
@@ -226,6 +227,31 @@ tune_cpu: true`,
 				require.Exactly(st, expected, c.Redpanda.KafkaAPI)
 			},
 		},
+		{
+			name: "extract kafka_api[].authentication_method",
+			key:  "redpanda.kafka_api",
+			value: `- name: external
+  address: 192.168.73.45
+  port: 9092
+  authentication_method: sasl
+- name: internal
+  address: 10.21.34.58
+  port: 9092
+`,
+			check: func(st *testing.T, c *Config) {
+				expected := []NamedAuthNSocketAddress{{
+					Name:    "external",
+					Address: "192.168.73.45",
+					Port:    9092,
+					AuthN:   &authNSasl,
+				}, {
+					Name:    "internal",
+					Address: "10.21.34.58",
+					Port:    9092,
+				}}
+				require.Exactly(st, expected, c.Redpanda.KafkaAPI)
+			},
+		},
 		{
 			name: "partially set map fields (json)",
 			key:  "redpanda.kafka_api",