Support multiple From addresses with random rotation per campaign

Currently, a campaign can only have a single From address. For example, a campaign can be configured as: From: Marketing <[email protected]> However, some email providers support multiple verified sender addresses, and it can be useful to distribute a campaign's messages across multiple senders. For example, I may want a single campaign to use: Marketing 1 <[email protected]> Marketing 2 <[email protected]> Marketing 3 <[email protected]> and have listmonk randomly select one of these addresses for each recipient. With the current single From address model, the only way to achieve this is to create multiple campaigns or implement the sending logic outside listmonk. Proposed feature Allow a campaign to configure multiple From addresses instead of only one. For example: From addresses: • Marketing 1 <[email protected]> • Marketing 2 <[email protected]> • Marketing 3 <marketing3@example…