[AgileConfig.Client] Use of Hard-coded Credentials in AgileConfig.Client

Hardcoded JWT Secret in AgileConfig <1.6.8 Server allows remote attackers to use the generated JWT token to gain administrator access.

References

• https://nvd.nist.gov/vuln/detail/CVE-2022-35540
• https://github.com/dotnetcore/AgileConfig/issues/91
• https://github.com/advisories/GHSA-mj5w-w588-j6xg