feat(schedule): show schedule errors

[wsan3]

Description

Whenever a user has a YAML bug in their pipeline, or any other build-breaking error that short-circuits pipeline execution, they can usually find these error in the Audit tab, where we populate the hook with the error message.

This is currently not available for schedules. Instead, the error is just logged.

Related

https://github.com/go-vela/community/issues/872

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 96.09%. Comparing base (fb4a95c) to head (ef91c0a).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #373   +/-   ##
=======================================
  Coverage   96.08%   96.09%           
=======================================
  Files          69       69           
  Lines        5361     5374   +13     
=======================================
+ Hits         5151     5164   +13     
  Misses        136      136           
  Partials       74       74           

Files	Coverage Δ
database/schedule.go	100.00% <100.00%> (ø)
library/schedule.go	100.00% <100.00%> (ø)