Dynamic Custom Severity Support for Toast Component in Styled Mode

[jhillacre]

In styled mode, the toast component currently uses hardcoded severity mappings (info, success, warn, error, secondary, contrast). This approach limits its extensibility and creates an inconsistency with components like message, which dynamically handles props.severity.

For reference, here is the relevant toast class function:
https://github.com/primefaces/primevue/blob/180c921c894f0537767c33b0568754c773caa960/packages/primevue/src/toast/style/ToastStyle.js#L267-L277

In contrast, the message component supports dynamic class generation. The root classes function evaluates props.severity and automatically generates corresponding classes without requiring predefined mappings. For reference:
https://github.com/primefaces/primevue/blob/180c921c894f0537767c33b0568754c773caa960/packages/primevue/src/message/style/MessageStyle.js#L305-L313

If this design choice was made to prevent automatic class purging, it would make sense to hardcode severities. However, since the message component's dynamic approach works as intended, this doesn't appear to be a concern.

This request is to update the toast styled mode class generation to use dynamic severity class generation. Doing so would:

• Promote the extensibility of toast in styled mode.
• Align its behaviour with components like message and inlinemessage.
• Simplify the process of extending toast with custom severities by removing the need for pt overrides when design token additions would otherwise suffice.

This enhancement request focuses on the toast component but could also extend to other components like badge and tag, which currently rely on hardcoded severities. Addressing these would further align with PrimeVue's philosophy of flexibility and extensibility.

Thank you for taking the time to read this enhancement request. I'd be happy to provide more details or examples.