feat: implement SCIM handler for SCIM 2.0 compliance (#25572)

Rewrites the SCIM 2.0 user provisioning handler to be RFC 7644
compliant. Verified against an external IdP Okta.

Behavior is OPT IN

enterprise/coderd/coderdenttest/coderdenttest.go

@@ -67,6 +67,7 @@ type Options struct {
 	BrowserOnly                bool
 	EntitlementsUpdateInterval time.Duration
 	SCIMAPIKey                 []byte
+	UseLegacySCIM              bool
 	UserWorkspaceQuota         int
 	ProxyHealthInterval        time.Duration
 	LicenseOptions             *LicenseOptions
@@ -108,6 +109,7 @@ func NewWithAPI(t *testing.T, options *Options) (
 		AuditLogging:               options.AuditLogging,
 		BrowserOnly:                options.BrowserOnly,
 		SCIMAPIKey:                 options.SCIMAPIKey,
+		UseLegacySCIM:              options.UseLegacySCIM,
 		DERPServerRelayAddress:     serverURL.String(),
 		DERPServerRegionID:         int(oop.DeploymentValues.DERP.Server.RegionID.Value()),
 		ReplicaSyncUpdateInterval:  options.ReplicaSyncUpdateInterval,