Map R2DBC Pool 'minIdle' property

Closes gh-32332

Author: snicoll

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/r2dbc/ConnectionFactoryBuilder.java

@@ -244,6 +244,8 @@ ConnectionPoolConfiguration connectionPoolConfiguration(ConnectionFactoryOptions
 					.to(builder::maxIdleTime);
 			map.from(options.getValue(PoolingConnectionFactoryProvider.MAX_CREATE_CONNECTION_TIME)).as(this::toDuration)
 					.to(builder::maxCreateConnectionTime);
+			map.from(options.getValue(PoolingConnectionFactoryProvider.MIN_IDLE)).as(this::toInteger)
+					.to(builder::minIdle);
 			map.from(options.getValue(PoolingConnectionFactoryProvider.POOL_NAME)).as(this::toString).to(builder::name);
 			map.from(options.getValue(PoolingConnectionFactoryProvider.PRE_RELEASE)).to((function) -> builder
 					.preRelease((Function<? super Connection, ? extends Publisher<Void>>) function));

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/r2dbc/ConnectionFactoryBuilderTests.java

@@ -265,7 +265,7 @@ private enum ExpectedOption {
 		MAX_CREATE_CONNECTION_TIME(PoolingConnectionFactoryProvider.MAX_CREATE_CONNECTION_TIME, Duration.ofSeconds(10),
 				"maxCreateConnectionTime"),
 
-		MIN_IDLE(PoolingConnectionFactoryProvider.MIN_IDLE, 0, "minIdle"),
+		MIN_IDLE(PoolingConnectionFactoryProvider.MIN_IDLE, 5, "minIdle"),
 
 		POOL_NAME(PoolingConnectionFactoryProvider.POOL_NAME, "testPool", "name"),