Generates workflow calculations on the resource.

Adds the following calculations (using add_new_calculation so user-defined calculations take precedence):

• :available_actions — list of user-facing transition names for the current step
• :steps — list of all workflow step names (static, same for every record)
• :current_step — the name of the workflow's current step
• :pending_deadlines — the timeouts ahead of the record in its current step
• :entered_current_state_at — only when a transition_log is configured