Add summary emails

[ArtOfCode-]

Adds content summary emails sent to staff. Helps in raising our email volume to avoid AWS issues...

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.50%. Comparing base (93b9fd9) to head (bb132a5).
Report is 13 commits behind head on develop.

Additional details and impacted files

Components	Coverage Δ
controllers	61.81% <ø> (ø)
helpers	69.29% <ø> (+0.11%)	⬆️
jobs	48.57% <100.00%> (+20.57%)	⬆️
models	81.92% <ø> (ø)

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[Oaphi]

Suggestions incoming shortly - it also seems it's the first time we've ever tried to pass ActiveRecord::Relation as a parameter to .with( - which I believe is not a supported type? Seems to be corroborated by the "Unsupported argument type: ActiveRecord::Relation" error when trying to implement tests.

#1667

[Oaphi]

tsck, seems like mail delivery test might need better isolation (or maybe not, the pipeline only complains about the recipient's email), CircleCI didn't like the merged version at all. Initially. Must be flaky. Yup, definitely flaky.

[Oaphi]

LGTM