Setting a requirement in YAML specs leads to no agent can build this job

Steps to Reproduce

1. Create a capability like: Executable >> Command capability called an executable
2. Create a YAML spec plan like the following:

   project:
     key: DRAGON
     plan:
       key: SLAYER
       name: Dragon Slayer Quest
   stages:
     - jobs:
         - scripts:
             - echo 'Hello world!'
           requirements:
             - an executable
   

Expected Results

The plan will be build and 'Hello world!' is displayed.

Actual Results

The plan will never build. It happens because of the missing requirement.

Notes

It is not clear anywhere that the user should use the capability class to define the requirements for a job. The docs will, in fact, lead them to a wrong conclusion that the same name used in the UI could be used in YAML.

This is part of the YAML reference about requirements:

Workaround

Use the full class name that specifies the capability. The name can be found by hovering the mouse in the capability Admin >> Overview >> Server capabilities >> (selected capability) and checking the name on browser status bar. Please notice that "+" (plus signs) need to be changed to spaces.