[WIP] More email template updates

[kieckhafer]

• Better email templates
• Subject now pulls from collection, is no longer hardcoded
• Fixes Ability to modify transactional email templates via the dashboard #1515 - remaining bullet points of 1515 are hit with this PR

[CLAassistant]

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1 out of 2 committers have signed the CLA.

✅ kieckhafer
❌ Erik Kieckhafer

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[kieckhafer]

Had some issues with CLA using a secondary account under my name (that i was unaware I had)... so we just created a new PR instead: #1585