feat(core): provide the ability to set custom headers on outgoing email messages #24278

[valentinogiardino]

Proposed Changes

• Introduced a new enum, WorkflowParameter, in WorkflowParameter.java to centralize common workflow actionlet parameters. This enum now defines the CUSTOM_HEADERS parameter with its key, description, default value, and requirement status.

• Updated various workflow actionlets—such as EmailActionlet, FourEyeApproverActionlet, MultipleApproverActionlet, NotifyAssigneeActionlet, NotifyUsersActionlet, and SendFormEmailActionlet—to utilize the new WorkflowParameter.CUSTOM_HEADERS. This change standardizes how custom email headers are defined and extracted.

• MailerTool Update: Updated the MailerTool to support customHeaders, ensuring that custom header functionality is available across all email-related tools.

• Modified the Mailer class to encapsulate header application logic in an applyHeaders method. This method now dynamically loads the system-wide default email headers via the new ConfigUtils.getDefaultEmailHeaders() method, allowing the default headers configuration to be changed at runtime.

• New Config Property: Added the DEFAULT_EMAIL_HEADERS configuration property. This property allows administrators to define system-wide email header defaults (formatted as a comma-separated list of header key/value pairs, e.g., "X-Custom-1:Value1, X-Custom-2:Value2"). When no custom headers are provided at the workflow level, these defaults are applied to all outgoing emails.

• Included additional validation and logging to capture and report any header parsing errors or invalid header lines.

Checklist

• Tests
• Translations
• Security Implications Contemplated (add notes if applicable)

Additional Info

This feature allows users to specify custom headers for workflow-triggered emails, useful for adding metadata or integration purposes (e.g., tracking headers, priority indicators).

Screenshots

Notify Assignee

Notify user

Async Send an Email

Send an Email

Multiple Approver

Four Eyes Approver

Send Form email

Mailer View Tool

Reset Password

This PR fixes: #24278

[dotcms-github-app]

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