Refactor OpenAiImageOptions and enhance test coverage

This commit makes several improvements to the OpenAiImageOptions class:

1. Remove all deprecated methods from OpenAiImageOptions.Builder:
   - Removed withN(), withModel(), withQuality(), withResponseFormat(),
     withWidth(), withHeight(), withStyle(), and withUser() methods
   - These were marked as @Deprecated(forRemoval = true, since = "1.0.0-M8")

2. Align OpenAiImageOptions structure with OpenAiChatOptions:
   - Added fromOptions() static method for creating copies
   - Added copy() instance method
   - Updated Builder class to match pattern in OpenAiChatOptions
   - Changed Builder field from private final to protected
   - Added Builder constructor that takes an existing options object

3. Enhance setSize() method to maintain consistency:
   - Updated setSize() to parse the size string and update width/height properties
   - Added proper error handling for invalid formats
   - Ensures consistent state between size, width, and height properties

4. Comprehensive test coverage improvements:
   - Added tests for builder pattern with all fields
   - Added tests for copy functionality
   - Added tests for all setter methods
   - Added tests for default values
   - Added tests for equals(), hashCode(), and toString() methods
   - Added specific tests for the updated setSize() behavior
   - Fixed test expectations to match actual implementation behavior

These changes improve code consistency, maintainability, and test coverage
while removing deprecated methods that were scheduled for removal.

Signed-off-by: jonghoonpark <dev@jonghoonpark.com>

spring-ai-docs/src/main/antora/modules/ROOT/pages/upgrade-notes.adoc

@@ -35,6 +35,12 @@ Hopefully Watson will reappear in a future version of Spring AI
 
 
 
+
+[[upgrading-to-1-0-0-RC1]]
+== Upgrading to 1.0.0-RC1
+
+
+
 [[upgrading-to-1-0-0-m8]]
 == Upgrading to 1.0.0-M8