Implicit 404 handlers cause panic if `Use` is called more than once

[aouji]

Hi team. #2996 added 404 handlers to groups as long as they have any other middlewares. This currently means any of the following scenarios would try to add duplicate route handlers and panic:

// 1
apiGroup := e.Group("/api")
apiGroup.Use(Middleware1)
apiGroup.Use(Middleware2) // panic: echo_route_not_found /api: adding duplicate route (same method+path) is not allowed

// 2
apiGroup := e.Group("/api", Middlware1) // Internally `Use` is called since there is a middleware
apiGroup.Use(Middleware2) // panic: echo_route_not_found /api: adding duplicate route (same method+path) is not allowed

// 3 This is my real world scenario
apiGroup := e.Group("/api", Middlware1) // Internally `Use` is called since there is a middleware
resource1Group := apiGroup.Group("/resource") // Internally `Use` is called since there is a middleware inherited from parent group
resource1Group.Use(Middleware2) // panic: echo_route_not_found /api/resource: adding duplicate route (same method+path) is not allowed

Workaround is to avoid using Use if there are already any middlewares attached to a group or its parent, or to turn off the behvaior by setting NoGroupAutoRegister404Routes to true.

Edit: I just noticed that AllowOverwritingRoute is true by default. I would still argue it is buggy to have code panic if it is not set to true and user is not explicitly adding 404 handlers...

[aldas]

This is fixed in v5.3.1 https://github.com/labstack/echo/releases/tag/v5.3.1