Replace logback-classic dependency with spring-boot-starter-logging (#696)

This will reduce the dependencies we have to keep up to date, as
Spring can maintain that.

We can instead focus on keeping Spring up to date and trust that
they are patching logback-classic as and when required.

Author: Adrian Clay

service/build.gradle

@@ -40,7 +40,7 @@ dependencies {
 	implementation ('org.springframework.boot:spring-boot-starter-webflux')
 
 	// Logging
-	implementation 'ch.qos.logback:logback-classic:1.4.14'
+	implementation 'org.springframework.boot:spring-boot-starter-logging'
 
 	// Infrastructure
 	implementation 'com.amazonaws:aws-java-sdk-s3:1.12.673'