[go-server] Change Routes type from `[]Route` to `map[string]Route`

Created by: lwj5

Since the operation ID should be unique for each API group, it is more rightly for the routes to be map[string]Route instead of the name being a field of Route.

Also, this allows for easy embedding compared to using []Route.

For example, if you wish to embed the controller and "override" a DeleteOrder you would have to "override" the whole Routes() method like so...

// Routes returns all of the api route for the StoreApiController
func (c *StoreApiController) Routes() Routes {
	return Routes{
		"DeleteOrder": Route{
			strings.ToUpper("Delete"),
			"/v2/store/order/{orderId}",
			c.DeleteOrder,
		},
		"GetInventory": Route{
			strings.ToUpper("Get"),
			"/v2/store/inventory",
			c.GetInventory,
		},
		"GetOrderById": Route{
			strings.ToUpper("Get"),
			"/v2/store/order/{orderId}",
			c.GetOrderById,
		},
		"PlaceOrder": Route{
			strings.ToUpper("Post"),
			"/v2/store/order",
			c.PlaceOrder,
		},
	}
}

Now with the new change, you may do:

// Routes returns all of the api route for the StoreApiController
func (c *StoreApiController) Routes() Routes {
	routes := c.StoreApiController.Routes() // Get "parent" Routes()
	routes["DeleteOrder"] = Route{
		strings.ToUpper("Delete"),
		"/v2/store/order/{orderId}",
		c.DeleteOrder,
	}
	return routes
}

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Hi @antihax @grokify @kemokemo @jirikuncar @ph4r5h4d, please help to take a look at this PR