Templating with `task.resolver_username` not working correctly

[rbeuque74]

Describe the bug
Templating with .task.resolver_username not working correctly with templating function.
resolver_username is a *string pointer and giving a pointer to templating function such as toString is returning a pointer value instead of the actual string.

Expected behavior
We should de-reference the pointer here :

utask/engine/values/values.go

Line 255 in 8540372

v.m[TaskKey] = t

And give a plain string value every time a string pointer is included into the values. As the task is only Golang model that we are including in the values, we should check at all the keys here.

utask version impacted by the bug
All

[rbeuque74]

cc @Alkorin