Streamline EmbeddingOptions

* Add model and dimensions to option abstraction
* Use abstraction in Observations directly instead of dedicated implementation
* Clean-up the merge of runtime and default embedding options in OpenAI

Relates to #gh-1148

Signed-off-by: Thomas Vitale <ThomasVitale@users.noreply.github.com>

models/spring-ai-postgresml/src/main/java/org/springframework/ai/postgresml/PostgresMlEmbeddingOptions.java

@@ -28,6 +28,7 @@ import org.springframework.ai.postgresml.PostgresMlEmbeddingModel.VectorType;
 
 /**
  * @author Christian Tzolov
+ * @author Thomas Vitale
  */
 @JsonInclude(Include.NON_NULL)
 public class PostgresMlEmbeddingOptions implements EmbeddingOptions {
@@ -130,4 +131,14 @@ public class PostgresMlEmbeddingOptions implements EmbeddingOptions {
 		this.metadataMode = metadataMode;
 	}
 
+	@Override
+	public String getModel() {
+		return null;
+	}
+
+	@Override
+	public Integer getDimensions() {
+		return null;
+	}
+
 }