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.

cli/testdata/server-config.yaml.golden

@@ -364,6 +364,11 @@ oidc:
   # Markdown format is supported.
   # (default: <unset>, type: string)
   signupsDisabledText: ""
+  # 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.
+  # (default: <unset>, type: bool)
+  dangerousSkipIssuerChecks: false
 # Telemetry is critical to our ability to improve Coder. We strip all personal
 # information before sending data to our servers. Please only disable telemetry
 # when required by your organization's security policy.