Add read_channel_content permission (#24118)

* Add read_channel_content permission

* fix tests

* update system console default permissions per role

* add read_channel_content to e2e defaultRolesPermissions

* Migration to include custom roles

* change deprecated isNotExactRole for isNotRole

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Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/webhook.go

@@ -775,7 +775,7 @@ func (a *App) HandleIncomingWebhook(c *request.Context, hookID string, req *mode
 		return model.NewAppError("HandleIncomingWebhook", "web.incoming_webhook.user.app_error", nil, "", http.StatusForbidden).Wrap(result.NErr)
 	}
 
-	if channel.Type != model.ChannelTypeOpen && !a.HasPermissionToChannel(c, hook.UserId, channel.Id, model.PermissionReadChannel) {
+	if channel.Type != model.ChannelTypeOpen && !a.HasPermissionToChannel(c, hook.UserId, channel.Id, model.PermissionReadChannelContent) {
 		return model.NewAppError("HandleIncomingWebhook", "web.incoming_webhook.permissions.app_error", nil, "", http.StatusForbidden)
 	}