Supporting custom error handling

[ndortega]

@louisponet

Below is an example of how you would disable the default error handling so far. It's worth noting that there is no default error handling for middleware functions.

What do you think? Does this solve the issue you brought up here: https://discourse.julialang.org/t/ann-oxygen-jl-v1-1-6-cron-scheduling/97291/3?u=ndortega

using Oxygen
using HTTP

@get "/" function(req::HTTP.Request)
    return "hello world!"
end

@get "/bad" function(req::HTTP.Request)
    throw("whoops")
    "hello"
end

function errorcatcher(handle)
    function(req)
        try 
            return  handle(req)
        catch e 
            return HTTP.Response(500, "here's a custom error response")
        end
    end
end

# start the web server
serve(middleware=[errorcatcher], catch_errors=false)