feat: implement disabling oidc issuer checks (#13991)

* use DANGEROUS prefix and drop a warning log

cli/testdata/coder_server_--help.golden

@@ -513,6 +513,12 @@ OIDC OPTIONS:
           The custom text to show on the error page informing about disabled
           OIDC signups. Markdown format is supported.
 
+      --dangerous-oidc-skip-issuer-checks bool, $CODER_DANGEROUS_OIDC_SKIP_ISSUER_CHECKS
+          OIDC issuer urls must match in the request, the id_token 'iss' claim,
+          and in the well-known configuration. This flag disables that
+          requirement, and can lead to an insecure OIDC configuration. It is not
+          recommended to use this flag.
+
 PROVISIONING OPTIONS: 
 Tune the behavior of the provisioner, which is responsible for creating,
 updating, and deleting workspace resources.