[feature/oidc] Add support for very basic RBAC (#2642)

* Add support for very basic RBAC

* Add some small tests for allowedGroup and adminGroup

* Switch to table-driven tests

internal/api/auth/callback_test.go

@@ -0,0 +1,45 @@
+package auth
+
+import (
+	"testing"
+
+	"github.com/superseriousbusiness/gotosocial/testrig"
+)
+
+func TestAdminGroup(t *testing.T) {
+	testrig.InitTestConfig()
+	for _, test := range []struct {
+		name     string
+		groups   []string
+		expected bool
+	}{
+		{name: "not in admin group", groups: []string{"group1", "group2", "allowedRole"}, expected: false},
+		{name: "in admin group", groups: []string{"group1", "group2", "adminRole"}, expected: true},
+	} {
+		test := test // loopvar capture
+		t.Run(test.name, func(t *testing.T) {
+			if got := adminGroup(test.groups); got != test.expected {
+				t.Fatalf("got: %t, wanted: %t", got, test.expected)
+			}
+		})
+	}
+}
+
+func TestAllowedGroup(t *testing.T) {
+	testrig.InitTestConfig()
+	for _, test := range []struct {
+		name     string
+		groups   []string
+		expected bool
+	}{
+		{name: "not in allowed group", groups: []string{"group1", "group2", "adminRole"}, expected: false},
+		{name: "in allowed group", groups: []string{"group1", "group2", "allowedRole"}, expected: true},
+	} {
+		test := test // loopvar capture
+		t.Run(test.name, func(t *testing.T) {
+			if got := allowedGroup(test.groups); got != test.expected {
+				t.Fatalf("got: %t, wanted: %t", got, test.expected)
+			}
+		})
+	}
+}