[BUG] No support for http urls in notification channels

[lezzago]

Describe the bug
The notification plugin does not support "http" urls for the notification channels like Webhook. The alerting plugin already supports this and breaks functionality when integrating with notification plugin.

To Reproduce
N/A

Expected behavior
The notification plugin should support "http" urls.

Plugins
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Screenshots
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Host/Environment (please complete the following information):

• OS: [e.g. iOS]
• Version [e.g. 22]

Additional context
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[zhongnansu]

I thought the original idea is to not support http, only support https. As code here suggests

[lezzago]

Currently Alerting plugin supports http, so this can break integration for some users