Deprecate R2dbcCustomConversions constructor taking Collection of converters.

Creating R2dbcCustomConversions without a dialect or StoreConversions can easily lead to misconfiguration that isn't immediately obvious because of missing store simple types. We now deprecated the constructor and have added guidance on how to properly create R2dbcCustomConversions that is associated with a dialect.

Closes #628

src/main/java/org/springframework/data/r2dbc/convert/MappingR2dbcConverter.java

@@ -70,7 +70,7 @@ public class MappingR2dbcConverter extends BasicRelationalConverter implements R
 	 */
 	public MappingR2dbcConverter(
 			MappingContext<? extends RelationalPersistentEntity<?>, ? extends RelationalPersistentProperty> context) {
-		super(context, new R2dbcCustomConversions(Collections.emptyList()));
+		super(context, new R2dbcCustomConversions(CustomConversions.StoreConversions.NONE, Collections.emptyList()));
 	}
 
 	/**

src/main/java/org/springframework/data/r2dbc/convert/R2dbcCustomConversions.java

@@ -41,7 +41,11 @@ public class R2dbcCustomConversions extends CustomConversions {
 	 * Create a new {@link R2dbcCustomConversions} instance registering the given converters.
 	 *
 	 * @param converters must not be {@literal null}.
+	 * @deprecated since 1.3, use {@link #of(R2dbcDialect, Object...)} or
+	 *             {@link #R2dbcCustomConversions(StoreConversions, Collection)} directly to consider dialect-native
+	 *             simple types. Use {@link CustomConversions.StoreConversions#NONE} to omit store-specific converters.
 	 */
+	@Deprecated
 	public R2dbcCustomConversions(Collection<?> converters) {
 		super(new R2dbcCustomConversionsConfiguration(STORE_CONVERSIONS, appendOverrides(converters)));
 	}

src/test/java/org/springframework/data/r2dbc/convert/MappingR2dbcConverterUnitTests.java

@@ -41,6 +41,7 @@ import org.springframework.core.convert.converter.Converter;
 import org.springframework.dao.InvalidDataAccessApiUsageException;
 import org.springframework.data.annotation.Id;
 import org.springframework.data.annotation.Transient;
+import org.springframework.data.convert.CustomConversions;
 import org.springframework.data.convert.ReadingConverter;
 import org.springframework.data.convert.WritingConverter;
 import org.springframework.data.r2dbc.mapping.OutboundRow;
@@ -62,7 +63,7 @@ public class MappingR2dbcConverterUnitTests {
 	@BeforeEach
 	void before() {
 
-		R2dbcCustomConversions conversions = new R2dbcCustomConversions(
+		R2dbcCustomConversions conversions = new R2dbcCustomConversions(CustomConversions.StoreConversions.NONE,
 				Arrays.asList(StringToMapConverter.INSTANCE, MapToStringConverter.INSTANCE,
 						CustomConversionPersonToOutboundRowConverter.INSTANCE, RowToCustomConversionPerson.INSTANCE));
 

src/test/java/org/springframework/data/r2dbc/mapping/R2dbcMappingContextUnitTests.java

@@ -45,7 +45,7 @@ public class R2dbcMappingContextUnitTests {
 	@Test
 	public void shouldCreateMetadataForConvertedTypes() {
 
-		R2dbcCustomConversions conversions = new R2dbcCustomConversions(
+		R2dbcCustomConversions conversions = new R2dbcCustomConversions(CustomConversions.StoreConversions.NONE,
 				Arrays.asList(ConvertedEntityToRow.INSTANCE, RowToConvertedEntity.INSTANCE));
 		R2dbcMappingContext context = new R2dbcMappingContext();
 		context.setSimpleTypeHolder(conversions.getSimpleTypeHolder());