feat(r/gnoland/home): add AdminSetOverride (#2583)

My goal was to implement this for Test 4, but the current upgrade
strategy does not include contract patching.

---------

Signed-off-by: moul <94029+moul@users.noreply.github.com>

examples/gno.land/r/gnoland/home/gno.mod

@@ -1,6 +1,7 @@
 module gno.land/r/gnoland/home
 
 require (
+	gno.land/p/demo/ownable v0.0.0-latest
 	gno.land/p/demo/ufmt v0.0.0-latest
 	gno.land/p/demo/ui v0.0.0-latest
 	gno.land/r/gnoland/blog v0.0.0-latest

examples/gno.land/r/gnoland/home/home.gno

@@ -3,6 +3,7 @@ package home
 import (
 	"std"
 
+	"gno.land/p/demo/ownable"
 	"gno.land/p/demo/ufmt"
 	"gno.land/p/demo/ui"
 	blog "gno.land/r/gnoland/blog"
@@ -12,7 +13,16 @@ import (
 // XXX: use an updatable block system to update content from a DAO
 // XXX: var blocks avl.Tree
 
+var (
+	override string
+	admin    = ownable.NewWithAddress("g1u7y667z64x2h7vc6fmpcprgey4ck233jaww9zq") // @manfred by default
+)
+
 func Render(_ string) string {
+	if override != "" {
+		return override
+	}
+
 	dom := ui.DOM{Prefix: "r/gnoland/home:"}
 	dom.Title = "Welcome to gno.land"
 	dom.Classes = []string{"gno-tmpl-section"}
@@ -267,3 +277,13 @@ func discoverLinks() ui.Element {
 </div><!-- end columns-3-->`),
 	}
 }
+
+func AdminSetOverride(content string) {
+	admin.AssertCallerIsOwner()
+	override = content
+}
+
+func AdminTransferOwnership(newAdmin std.Address) {
+	admin.AssertCallerIsOwner()
+	admin.TransferOwnership(newAdmin)
+}

examples/gno.land/r/gnoland/home/overide_filetest.gno

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"std"
+
+	"gno.land/p/demo/testutils"
+	"gno.land/r/gnoland/home"
+)
+
+func main() {
+	std.TestSetOrigCaller("g1u7y667z64x2h7vc6fmpcprgey4ck233jaww9zq")
+	home.AdminSetOverride("Hello World!")
+	println(home.Render(""))
+	home.AdminTransferOwnership(testutils.TestAddress("newAdmin"))
+	defer func() {
+		r := recover()
+		println("r: ", r)
+	}()
+	home.AdminSetOverride("Not admin anymore")
+}
+
+// Output:
+// Hello World!
+// r:  unauthorized; caller is not owner