Add automated exam announcement via Discord

[AxonC]

Context

Examiners often have to craft a manual post on Discord to notify of exams, tagging in certain groups in the process. There is a Discord role, which has an ID, that is mentioned.

This doesn't happen for every exam, but is usually announced at some point before

Behaviour description

### Acceptance Criteria

AS a practical examiner I can post an automated notification of an upcoming exam

(Must have requirements unless otherwise specified)

• Within the 'Exam Setup' page of the training panel, add an action in the 'Accepted Exams' for any of the examiners assigned to post an automated notification to Discord.
• The action should allow the examiner to add additional notes to the announcement.
• The notification should contain the position, the scheduled time of the exam (in both Z and local time) and any notes the the examiner wishes to append to the announcement
• This should post into a channel (configured via an environment / config variable) using the functions found in the Discord class in the libraries folder
• Could have: The message should mention a role (configured via an environment / config variable) via the Discord API

[linear]

TECH-479

[CLC0609]

I can take