Fix 400 return code on SAF errors

[richard-salac]

Describe the bug
This is a complementary issue to #3007

There is the mapping between SAF errors and http return codes with one specific handling for error 8/16/28 mapped to 400. It is the only one SAF error with distinguished return code with seemingly no specific reason. I suggest to unify the error mapping to 500.

api-layer/common-service-core/src/main/java/org/zowe/apiml/passticket/AbstractIRRPassTicketException.java

Line 65 in 32793d8

ERR_8_16_28(8, 16, 28, HttpStatus.SC_BAD_REQUEST, "Unable to generate PassTicket. Verify that the secured signon (PassTicket) function and application ID is configured properly by referring to Using PassTickets in z/OS Security Server RACF Security Administrator's Guide."),

Expected behavior
Return 500 as for the other SAF error messages as 400 should indicate malformed request rather than permissions issue

Details

• Version and build number: v3, v2