Share events for audit logging

[kobergj]

Contains lifecyle events for shares and links for now.

List of sharing events:

		events.ShareCreated{},
		events.ShareUpdated{},
		events.ShareRemoved{},
		events.ReceivedShareUpdated{},
		events.LinkCreated{},
		events.LinkUpdated{},
		events.LinkRemoved{},
		events.LinkAccessed{},
		events.LinkAccessFailed{},

see details in pkg/events/types.go

Does not include federated shares in this PR

[update-docs]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would create a changelog item based on your changes.