[REQ] [Postgresql] Instead of serial use identity

Why not use identity for serial .

The serial in the PostgreSQl wiki is marked as anti pattern also,

The serial types have some weird behaviors that make schema, dependency, and permission management unnecessarily cumbersome.

Describe the solution you'd like

openapi-generator/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PostgresqlSchemaCodegen.java

Line 53, 54
Block ine 525-550 change the logic to use identity

Something like this

         if (colName.equals("id") && Boolean.valueOf(additionalProperties.get(ID_AUTOINC_ENABLED).toString())) {
                    columnDefinition.put("colDataType", "BIGINT GENERATED ALWAYS AS IDENTITY");
                } else {
                    columnDefinition.put("colDataType", "BIGINT");
                }

---
        if (colName.equals("id") && Boolean.valueOf(additionalProperties.get(ID_AUTOINC_ENABLED).toString())) {
                    if (colDataType.equals("BIGINT")) {
                        colDataType = "BIGINT GENERATED ALWAYS AS IDENTITY";
                  
                }

---
if (!columnDefinition.get("colDataType").equals("BIGINT GENERATED ALWAYS AS IDENTITY")
            ) { // No default value for autoincremented
            // IDs

Start in openapi-generator/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PostgresqlSchemaCodegen.java, especially lines 53-54 and the logic around lines 525-550. Trace how the ID_AUTOINC_ENABLED property affects column definitions and default values, then confirm that generated PostgreSQL schemas use BIGINT GENERATED ALWAYS AS IDENTITY for enabled autoincrement IDs without adding an inappropriate default.