Show a confirmation prompt as an action before proceeding

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Is your feature request related to a problem? Please describe.
I would like to create confirmation prompts that ask the user if he really wants to proceed with an operation.
The prompt would display a custom message with an OK and Cancel buttons.

Describe the solution you'd like
For example:

<prompt type="okcancel" name="proceed" title="Are you sure you want to proceed with the operation?" onok="/continue" oncancel="/abort" failoncancel="true" />

If the user has selected OK, the property proceed should be set to value /continue.
If the user has selected Cancel, the property proceed should be set to value /abort.
If the attribute failoncancel is set to true, the action should fail if the user has clicked on Cancel button.

Describe alternatives you've considered
There does not seems to exists an action that can cancel the operation.

Additional context
N/A

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Another alternative solution would be to implement a <fail /> action.
The action could have multiple different attributes to fail the action based on different criteria.

To get a confirmation message before proceeding, one could do something like :

<prompt type="yesno" name="proceed" title="Are you sure you want to proceed with the operation?"
        valueyes="true" valueno="false" />
<fail iffalse="${proceed}" />
<exec path="..." />

The above example would fail since the property proceed is set to false when one answer "no" the to prompt message.
If the user select yes, the property proceed is set to true which does not fail the <fail/> action and the execution continue to the next action.

Other possible attributes includes :

• ifset, fails the action if the given property name is set.
• ifunset, fails the action of the given property name is unset.
• ifempty, fails the action of the given value is empty.
• ifnotempty, fails the action of the given value is not empty.
• iftrue, fails the action if the given value evaluates to true. For example 1, true, t, yes or y (case insensitive).
• iffalse, fails the action if the given value evaluates to false. For example 0, false, f, no or n (case insensitive).
• inverse, same as attribute.
• exprtk, fails the action of the given exprtk expression evaluates to true.

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The xml element should be named <stop> instead of <fail> to indicate that it is a command and not a fatality.