Added an action proposal relevant for increasingly popular Testcontainers projects

Author: mstahv

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/DataSourceBeanCreationFailureAnalyzer.java

@@ -66,6 +66,8 @@ private String getAction(DataSourceBeanCreationException cause) {
 		StringBuilder action = new StringBuilder();
 		action.append(String.format("Consider the following:%n"));
 		if (EmbeddedDatabaseConnection.NONE == cause.getConnection()) {
+			action.append(String
+					.format("\tIf you're using Testcontainers to set up your development datasource, consider starting the application from the test sources instead.%n"));
 			action.append(String
 				.format("\tIf you want an embedded database (H2, HSQL or Derby), please put it on the classpath.%n"));
 		}