feat(panel): add domain-admin role with per-domain authorization

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/web/handlers/authz.go

@@ -0,0 +1,65 @@
+package handlers
+
+import (
+	"net/http"
+
+	"github.com/mixeme/selfpost/internal/store"
+	"github.com/mixeme/selfpost/internal/web/auth"
+)
+
+func (h *Handlers) principal(r *http.Request) (auth.Principal, bool) {
+	return auth.PrincipalFromRequest(r)
+}
+
+func (h *Handlers) requireGlobal(w http.ResponseWriter, r *http.Request) (auth.Principal, bool) {
+	p, ok := h.principal(r)
+	if !ok || !p.IsGlobal() {
+		http.NotFound(w, r)
+		return auth.Principal{}, false
+	}
+	return p, true
+}
+
+func (h *Handlers) pageBase(r *http.Request) map[string]any {
+	p, _ := h.principal(r)
+	return map[string]any{
+		"User":     auth.CurrentUser(r),
+		"IsGlobal": p.IsGlobal(),
+	}
+}
+
+func (h *Handlers) assignedDomains(p auth.Principal) ([]store.Domain, error) {
+	if p.IsGlobal() {
+		return h.store.ListDomains()
+	}
+	all, err := h.store.ListDomains()
+	if err != nil {
+		return nil, err
+	}
+	var out []store.Domain
+	for _, d := range all {
+		if p.CanAccessDomain(d.ID) {
+			out = append(out, d)
+		}
+	}
+	return out, nil
+}
+
+func domainNameSet(domains []store.Domain) map[string]bool {
+	m := make(map[string]bool, len(domains))
+	for _, d := range domains {
+		m[d.Name] = true
+	}
+	return m
+}
+
+func domainIDSet(p auth.Principal) map[int64]bool {
+	if p.IsGlobal() {
+		return nil
+	}
+	m := make(map[int64]bool, len(p.Domains))
+	for _, id := range p.Domains {
+		m[id] = true
+	}
+	return m
+}