Add template function to link to other tasks

[JeanMertz]

It'd be nice if you could use a template function add links to other tasks in your task output.

For example, say a task shows a list of customer capabilities, it could then show it as this:

---

Capabilities:

• is_awesome _revoke
• has_pizzazz _revoke
• can_💃🏽 _revoke

---

With the revoke links linking to another task that allows you to remove capabilities from a customer.

The link would have to support the following:

• Link to an existing task.
• Optionally pre-fill variable values.

I don't know what the best way to do this is, but perhaps links could look something like [revoke][automaat:task id:12 variable:Var Name=value here variable:Variable 2=value]

• [revoke] will be the link text.
• automaat:task is a special prefix to let the parser know it should link to an existing Automaat task (we could add more automaat:... links later, if required, for example linking to search results).
• id:12 is the ID of the task to link to. We could instead use task names here, but then renaming a task would break this.
• variable:name=value is an optional (repeatable) pre-filled variable value.

(see next comment)

[JeanMertz]

Actually, I think we can write a custom Tera function for this, and have it fit with all the other templating support we have.

So you'd do something like [revoke]({{ task_url(id=12, variables=["Var Name=value", "Variable 2=value"]) }}), although I'm not yet sure if/how functions can support a vector as an input value, but we can experiment with that.