Add ability to set person hours at single session level

Feature Request: would like ability to set a persons hours at single session level *use case: volunteer has a one-off drs appointment and instead of being available for entire shift 1-5 they are available 2:30-5. This needs to be communicated to the Team Captain who writes up the lesson board for the afternoon.

Feature Request: would like ability to set a persons hours at single session level *use case: volunteer has a one-off drs appointment and instead of being available for entire shift 1-5 they are available 2:30-5. This needs to be communicated to the Team Captain who writes up the lesson board for the afternoon.