Deprecate support for theme

As seen in gh-28868, the support for Themes is now deprecated as of
Spring Framework 6.0 and will be removed in a future release.

Closes gh-29114

spring-context/src/main/java/org/springframework/ui/context/HierarchicalThemeSource.java

@@ -24,7 +24,9 @@ import org.springframework.lang.Nullable;
  *
  * @author Jean-Pierre Pawlak
  * @author Juergen Hoeller
+ * @deprecated as of 6.0, with no concrete replacement
  */
+@Deprecated
 public interface HierarchicalThemeSource extends ThemeSource {
 
 	/**

spring-context/src/main/java/org/springframework/ui/context/Theme.java

@@ -28,7 +28,9 @@ import org.springframework.context.MessageSource;
  * @since 17.06.2003
  * @see ThemeSource
  * @see org.springframework.web.servlet.ThemeResolver
+ * @deprecated as of 6.0, with no direct replacement
  */
+@Deprecated
 public interface Theme {
 
 	/**

spring-context/src/main/java/org/springframework/ui/context/ThemeSource.java

@@ -26,7 +26,9 @@ import org.springframework.lang.Nullable;
  * @author Jean-Pierre Pawlak
  * @author Juergen Hoeller
  * @see Theme
+ * @deprecated as of 6.0, with no direct replacement
  */
+@Deprecated
 public interface ThemeSource {
 
 	/**

spring-context/src/main/java/org/springframework/ui/context/support/DelegatingThemeSource.java

@@ -31,7 +31,9 @@ import org.springframework.ui.context.ThemeSource;
  * @author Juergen Hoeller
  * @since 1.2.4
  * @see UiApplicationContextUtils
+ * @deprecated as of 6.0, with no direct replacement
  */
+@Deprecated
 public class DelegatingThemeSource implements HierarchicalThemeSource {
 
 	@Nullable

spring-context/src/main/java/org/springframework/ui/context/support/ResourceBundleThemeSource.java

@@ -42,7 +42,9 @@ import org.springframework.ui.context.ThemeSource;
  * @see #setBasenamePrefix
  * @see java.util.ResourceBundle
  * @see org.springframework.context.support.ResourceBundleMessageSource
+ * @deprecated as of 6.0, with no direct replacement
  */
+@Deprecated
 public class ResourceBundleThemeSource implements HierarchicalThemeSource, BeanClassLoaderAware {
 
 	protected final Log logger = LogFactory.getLog(getClass());

spring-context/src/main/java/org/springframework/ui/context/support/SimpleTheme.java

@@ -26,7 +26,9 @@ import org.springframework.util.Assert;
  *
  * @author Juergen Hoeller
  * @since 17.06.2003
+ * @deprecated as of 6.0, with no concrete replacement
  */
+@Deprecated
 public class SimpleTheme implements Theme {
 
 	private final String name;

spring-context/src/main/java/org/springframework/ui/context/support/UiApplicationContextUtils.java

@@ -31,7 +31,9 @@ import org.springframework.ui.context.ThemeSource;
  * @author Jean-Pierre Pawlak
  * @author Juergen Hoeller
  * @since 17.06.2003
+ * @deprecated as of 6.0, with no direct replacement
  */
+@Deprecated
 public abstract class UiApplicationContextUtils {
 
 	/**