change: replace template with config headers

examples/demo-with-go-plugin/testcases/requests.yml

@@ -5,6 +5,8 @@ config:
         foo2: config_bar2
         expect_foo1: config_bar1
         expect_foo2: config_bar2
+    headers:
+        User-Agent: funplugin/${get_version()}
     verify: False
     export: ["foo3"]
 
@@ -22,8 +24,6 @@ teststeps:
             foo1: $foo1
             foo2: $foo2
             sum_v: $sum_v
-        headers:
-            User-Agent: funplugin/${get_version()}
     extract:
         foo3: "body.args.foo2"
     validate:
@@ -40,7 +40,6 @@ teststeps:
         method: POST
         url: $base_url/post
         headers:
-            User-Agent: funplugin/${get_version()}
             Content-Type: "text/plain"
         body: "This is expected to be sent back as part of response body: $foo1-$foo2-$foo3."
     validate:
@@ -54,7 +53,6 @@ teststeps:
         method: POST
         url: $base_url/post
         headers:
-            User-Agent: funplugin/${get_version()}
             Content-Type: "application/x-www-form-urlencoded"
         body: "foo1=$foo1&foo2=$foo2&foo3=$foo3"
     validate: