- relations to all hours with meeting date within the semester
- scaffold empty semesterFeedback record for each mission related
- build the SemesterProcessMail.kind == :mail for the initial mail

feat(semester-process-volunteer): builder that assigns the elegible missions from the volunteer to the SemesterProcessVolunteerMission join table relation

add attr-acessor for selected, in order to be able to filter form selected volunteers on select in form

fix(volunteer-semester-process-elegible): fix have_semester_process with doing subselect, because it didnt work otherwise

feat(semester-process-elegible-volunteer): add method semester_process_eligible that joins and groups the relevant scopes for semester process volunteers

feat(semester-process-elegible-volunteer): add scope that selects volunteers that where with active assignments or group assignments within the given semester

feat(semester-process-elegible-volunteer): add scope that gets volunteers wit a assignment or group assignment that has started, ever

feat(semester-process-elegible-volunteer): add scope that returns volunteers that dont have a semester process for given semester

feat(semester_process): add the duplication of the mission relation logic and validation into a concern

- call it mission

- they where useing date_between instead of date_between_inclusion

^

tidy volunteers complicated with_billable_hours_scope up and add a test for not including billed again hours

use advanced instead of duration, as it is more timezone safe

fix and make tests with Time more explicit and timezone safe

fix format helper test

fix format helper test

remove tz_parse helper

- so that the user can change the selection made on /billing_expenses
- so that the filter respects billeable records, and not billed as it was
  probably by mistake before

- if the query result delivers hour_ids array, query Hours directly by ids
- in case there is no hour_ids in the query result get hours the same way as before

- convert the scope into method, in order to make use of other model methods
- LEFT OUTER JOIN query, in order to be able to get full query features
- add ARRAY_AGG() functions to select, in order to have hour.id and hour.meeting_date
  in an array within the query result
- exclude volunteers who allready have a billing expense in the given period

- use the methods in BillingExpenseSemesterUtils
- shorten and slicken the whole method