chore: move template context (#8663)

The template module now holds the **Template** context, this makes it possible for (render) function in the template module to access functions and share data between render functions.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/8663
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Reviewed-by: Lucas <sclu1034@noreply.codeberg.org>
Co-authored-by: Gusted <postmaster@gusted.xyz>
Co-committed-by: Gusted <postmaster@gusted.xyz>

modules/templates/context_test.go

@@ -0,0 +1,18 @@
+// Copyright 2025 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: GPL-3.0-or-later
+package templates
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestContext(t *testing.T) {
+	type ctxKey struct{}
+
+	// Test that the original context is used for its context functions.
+	ctx := NewContext(context.WithValue(t.Context(), ctxKey{}, "there"))
+	assert.Equal(t, "there", ctx.Value(ctxKey{}))
+}