Wrong response code on login on the API Catalog over the Spring Cloud Gateway

[pj892031]

Describe the bug
We have an environment of Zowe v3 with Spring Cloud Gateway, Discovery, ZUUL Gateway, and z/OSMF. The authentication provider in the ZUUL cloud gateway was set but not working well. Once we tried to log in to the API Catalog (routed through Spring Cloud Gateway) the response call on the login request was 403 instead of 503.

Steps to Reproduce

1. Run Zowe v3 with the same configuration issue as in Authentication provider looks available even the communication between Gateway and z/OSMF is not working #3557 (static onboarded z/OSMF over AT-TLS with HTTPs address)
2. Open the API Catalog home page (routed by Spring Cloud Gateway)
3. Try to log in (with the correct credentials)

Expected behavior
The call ended with response code 503 (z/OSMF is actually not accessible), but there was 403.

https://github.com/zowe/api-layer/wiki/Issue-management