[PM-30613] Remove unused mjml-based-email-templates feature flag

[trmartin4]

🎟️ Tracking

https://bitwarden.atlassian.net/browse/PM-30613

📔 Objective

The mjml-based-email-templates flag was used to gate which method we used to send the Send OTP emails, as when we developed it we weren't sure whether MJML email services were going to be ready.

Since they are ready for use, and the Send OTP email work is still in development to be consumed by the Tools team, adding this feature flag was not necessary and adds additional complexity and permutations to their testing. Rather than having Tools test with the flag off then the flag on, we'll just have it on to begin with and they'll use the new email as the basis for their testing.

⏰ Reminders before review

• Contributor guidelines followed
• All formatters and local linters executed and passed
• Written new unit and / or integration tests where applicable
• Protected functional changes with optionality (feature flags)
• Used internationalization (i18n) for all UI strings
• CI builds passed
• Communicated to DevOps any deployment requirements
• Updated any necessary documentation (Confluence, contributing docs) or informed the documentation team

🦮 Reviewer guidelines

• 👍 (:+1:) or similar for great changes
• 📝 (:memo:) or ℹ️ (:information_source:) for notes or general info
• ❓ (:question:) for questions
• 🤔 (:thinking:) or 💭 (:thought_balloon:) for more open inquiry that's not quite a confirmed issue and could potentially benefit from discussion
• 🎨 (:art:) for suggestions / improvements
• ❌ (:x:) or ⚠️ (:warning:) for more significant problems or concerns needing attention
• 🌱 (:seedling:) or ♻️ (:recycle:) for future improvements or indications of technical debt
• ⛏ (:pick:) for minor or nitpick changes

[github-actions]

Checkmarx One – Scan Summary & Details – ebdc49f8-5b81-48d6-882a-5ad81ed9c37e

New Issues (2)

Checkmarx found the following issues in this Pull Request

#	Severity	Issue	Source File / Package	Checkmarx Insight
1		CSRF	/src/Api/Auth/Controllers/AccountsController.cs: 291	details Method at line 291 of /src/Api/Auth/Controllers/AccountsController.cs gets a parameter from a user request from model. This parameter value flow... Attack Vector
2		CSRF	/src/Api/Auth/Controllers/AccountsController.cs: 452	details Method at line 452 of /src/Api/Auth/Controllers/AccountsController.cs gets a parameter from a user request from model. This parameter value flow... Attack Vector

Fixed Issues (29)

Great job! The following issues were fixed in this Pull Request

Severity	Issue	Source File / Package
	CSRF	/src/Api/Tools/Controllers/SendsController.cs: 68
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 1428
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 1428
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 1428
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 1403
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 1527
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 1457
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 1311
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 847
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 847
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 1457
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 775
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 807
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 807
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 775
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 1403
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 293
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 1088
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 1508
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 245
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 161
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 191
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 216
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 1457
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 1017
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 732
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 1050
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 1160
	CSRF	/src/Api/Vault/Controllers/CiphersController.cs: 293

[codecov]

Codecov Report

❌ Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 56.06%. Comparing base (51aa419) to head (7012fb7).

Files with missing lines	Patch %	Lines
src/Core/Platform/Mail/HandlebarsMailService.cs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6889      +/-   ##
==========================================
- Coverage   60.01%   56.06%   -3.96%     
==========================================
  Files        1971     1971              
  Lines       87090    87060      -30     
  Branches     7759     7758       -1     
==========================================
- Hits        52266    48809    -3457     
- Misses      32928    36443    +3515     
+ Partials     1896     1808      -88     

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[trmartin4]

@ike-kottlowski as discussed, I removed the old Handlebars templates and renamed the v2 ones.

[trmartin4]

Had to resolve a merge conflict.