chore: support multi-org group sync with runtime configuration (#14578)

- Implement multi-org group sync
- Implement runtime configuration to change sync behavior
- Legacy group sync migrated to new package

enterprise/coderd/enidpsync/groups.go

@@ -0,0 +1,70 @@
+package enidpsync
+
+import (
+	"context"
+	"net/http"
+
+	"github.com/golang-jwt/jwt/v4"
+
+	"github.com/coder/coder/v2/coderd/idpsync"
+	"github.com/coder/coder/v2/codersdk"
+)
+
+func (e EnterpriseIDPSync) GroupSyncEnabled() bool {
+	return e.entitlements.Enabled(codersdk.FeatureTemplateRBAC)
+}
+
+// ParseGroupClaims parses the user claims and handles deployment wide group behavior.
+// Almost all behavior is deferred since each organization configures it's own
+// group sync settings.
+// GroupAllowList is implemented here to prevent login by unauthorized users.
+// TODO: GroupAllowList overlaps with the default organization group sync settings.
+func (e EnterpriseIDPSync) ParseGroupClaims(ctx context.Context, mergedClaims jwt.MapClaims) (idpsync.GroupParams, *idpsync.HTTPError) {
+	if !e.GroupSyncEnabled() {
+		return e.AGPLIDPSync.ParseGroupClaims(ctx, mergedClaims)
+	}
+
+	if e.GroupField != "" && len(e.GroupAllowList) > 0 {
+		groupsRaw, ok := mergedClaims[e.GroupField]
+		if !ok {
+			return idpsync.GroupParams{}, &idpsync.HTTPError{
+				Code:             http.StatusForbidden,
+				Msg:              "Not a member of an allowed group",
+				Detail:           "You have no groups in your claims!",
+				RenderStaticPage: true,
+			}
+		}
+		parsedGroups, err := idpsync.ParseStringSliceClaim(groupsRaw)
+		if err != nil {
+			return idpsync.GroupParams{}, &idpsync.HTTPError{
+				Code:             http.StatusBadRequest,
+				Msg:              "Failed read groups from claims for allow list check. Ask an administrator for help.",
+				Detail:           err.Error(),
+				RenderStaticPage: true,
+			}
+		}
+
+		inAllowList := false
+	AllowListCheckLoop:
+		for _, group := range parsedGroups {
+			if _, ok := e.GroupAllowList[group]; ok {
+				inAllowList = true
+				break AllowListCheckLoop
+			}
+		}
+
+		if !inAllowList {
+			return idpsync.GroupParams{}, &idpsync.HTTPError{
+				Code:             http.StatusForbidden,
+				Msg:              "Not a member of an allowed group",
+				Detail:           "Ask an administrator to add one of your groups to the allow list.",
+				RenderStaticPage: true,
+			}
+		}
+	}
+
+	return idpsync.GroupParams{
+		SyncEnabled:  true,
+		MergedClaims: mergedClaims,
+	}, nil
+}