feat: Support for form actions on submissions

[seangray-dev]

Description Our platform currently lacks the capability for users to define the action attribute in their HTML forms. Enabling this feature will empower our users, especially those without technical expertise in JavaScript, to directly specify a custom submission endpoint for their forms. This is particularly beneficial for users who prefer not to use JavaScript or our specific form handling libraries.

Proposed Change We propose to implement functionality that allows users to specify their submission endpoint directly within an HTML form via the action attribute. For example, users can set up their form as follows:

<form action="https://formail.dev/submit/<form-id>" method="post">
    <!-- form elements here -->
    <button type="submit">Submit</button>
</form>

Expected Benefits This update will offer several advantages:

• Flexibility and Ease of Use: Users gain the ability to integrate their forms with our backend by simply adjusting the HTML, making the platform more accessible to non-developers.
• Standard Compliance: Aligns our service with common web standards, enhancing compatibility with various web development tools and practices.
• Increased Customization: Users can integrate with other services or manage multiple forms by directing submissions to different endpoints without altering the backend logic.

Considerations Security Measures: We must ensure that action URLs are strictly validated to prevent submissions to unauthorized endpoints. Compatibility with Security Protocols: The implementation should maintain compatibility with CORS and CSRF protections to safeguard against common web vulnerabilities. Analytics Integrity: We need to assess the impact on our analytics and tracking systems to ensure that submission data remains accurate and actionable.

[seangray-dev]

Documentation will also need to be updated to reflect that we support this