feat(chequebook): add funding URL for mainnet users (#5284)

Co-authored-by: Copilot <[email protected]>

Author: akrem-chabchoub

pkg/settlement/swap/chequebook/init.go

@@ -98,9 +98,16 @@ func checkBalance(
 				msg := fmt.Sprintf("cannot continue until there is at least min %s available on address", swarmTokenName)
 				logger.Warning(msg, "min_amount", neededERC20, "address", overlayEthAddress)
 			}
+
 			if chainId == chaincfg.Testnet.ChainID {
 				logger.Warning("learn how to fund your node by visiting our docs at https://docs.ethswarm.org/docs/installation/fund-your-node")
 			}
+
+			if chainId == chaincfg.Mainnet.ChainID {
+				fundingURL := fmt.Sprintf("https://fund.ethswarm.org/?destination=%s&intent=initial-funding", overlayEthAddress.Hex())
+				logger.Info(fmt.Sprintf("fund your node using the funding URL: %s", fundingURL))
+			}
+
 			select {
 			case <-time.After(balanceCheckBackoffDuration):
 			case <-timeoutCtx.Done():