upgrade to use testfixtures v3 (#11904)

* upgrade to use testfixtures v3

* simplify logic

* make vendor

* update per @lunny

* Update templates/repo/empty.tmpl

* Update templates/repo/empty.tmpl

Co-authored-by: Lauris BH <lauris@nix.lv>

vendor/github.com/go-testfixtures/testfixtures/v3/json.go

@@ -0,0 +1,44 @@
+package testfixtures
+
+import (
+	"database/sql/driver"
+	"encoding/json"
+)
+
+var (
+	_ driver.Valuer = jsonArray{}
+	_ driver.Valuer = jsonMap{}
+)
+
+type jsonArray []interface{}
+
+func (a jsonArray) Value() (driver.Value, error) {
+	return json.Marshal(a)
+}
+
+type jsonMap map[string]interface{}
+
+func (m jsonMap) Value() (driver.Value, error) {
+	return json.Marshal(m)
+}
+
+// Go refuses to convert map[interface{}]interface{} to JSON because JSON only support string keys
+// So it's necessary to recursively convert all map[interface]interface{} to map[string]interface{}
+func recursiveToJSON(v interface{}) (r interface{}) {
+	switch v := v.(type) {
+	case []interface{}:
+		for i, e := range v {
+			v[i] = recursiveToJSON(e)
+		}
+		r = jsonArray(v)
+	case map[interface{}]interface{}:
+		newMap := make(map[string]interface{}, len(v))
+		for k, e := range v {
+			newMap[k.(string)] = recursiveToJSON(e)
+		}
+		r = jsonMap(newMap)
+	default:
+		r = v
+	}
+	return
+}