Event: set `occurredAt` as required, correct Event Status to `Started`, `Ended`, and add `eventType` in the header

[chicco785]

Description

Event: set occurredAt as required

Changes Made

• Event: set occurredAt as required
• EventStatus: EVENT_STATUS_ACTIVE -> EVENT_STATUS_STARTED
• EventStatus: EVENT_STATUS_COMPLETE -> EVENT_STATUS_ENDED
• Event / GridEvent: add eventType in the header.

Related Issues

Fixes #22

Checklist

• [x] I have used a PR title that is descriptive enough for a release note.
• [x] I have tested these changes locally.
• [x] I have added appropriate tests or updated existing tests.
• [x] I have tested these changes on a dedicated VM or a customer VM [name of the VM]
• [x] I have added appropriate documentation or updated existing documentation.

[barecheck[bot]]

Barecheck - Code coverage report

Total: 22.15% Your code coverage diff: 0.00% ▴

Uncovered files and lines

File	Lines
pkg/grid/v1/event.pb.go	55-59, 61-63, 65-67, 69-71, 73-75, 78-80, 107-111, 113-115, 117-119, 121-123, 130-132, 157-159, 161, 176-178, 180-184, 187-191, 194-198, 201-205, 208-212, 215-219, 222-226, 278-282, 308-317