[Notifications] Add Template Render Error Handling

[ScriptedBro]

Type

Task

Estimated Effort

1-3 development days

Summary

Return structured errors when notification templates are missing required variables or fail rendering.

Scope

apps/backend/notifications/templates/, apps/backend/notifications/email/index.ts

Required Data Structure

export interface TemplateRenderResult { html?: string; text?: string; error?: string }

Implementation Tasks

• Validate required template variables before rendering.
• Avoid sending partially rendered emails.
• Add tests for valid and missing-variable renders.
• Keep the change scoped to the listed files or the smallest adjacent module needed.
• Follow existing API response, contract error, and event naming conventions.

Acceptance Criteria

• The feature or fix is implemented with no new difficulty labels.
• Unit or contract tests cover the success path and at least one failure path.
• Any new migration, environment variable, or event shape is documented near the affected service or contract.

[Malcolm-Wander]

@Malcolm-Wander has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hello maintainer, I’d love to work on this issue please…I promise to do a swift and accurate job…thank you.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Malcolm-Wander to this issue.

[ochemegina-ai]

@ochemegina-ai has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Goodday maintainer I can fix this?

ℹ️ Repo Maintainers: To accept this application, review their application or assign @ochemegina-ai to this issue.

[drips-wave]

Congratulations, @ochemegina-ai! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @ochemegina-ai: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

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