Create a publisher for seq

[Franklin89]

Looking for suggestions and feedback on this. Also for the message template, I am unsure about a good message that could be displayed.

Usage:

services.AddHealthChecks()
    .AddSqlServer(configuration.GetConnectionString("DefaultConnection"))
    .AddSeqPublisher(options => 
    {
       options.Endpoint = configuration["Seq:Endpoint"];
       options.ApiKey = configuration["Seq:Apikey"];
     });

Dashboards similar to the ones described for App Insights can be created:

[unaizorrilla]

Hi @Franklin89

Let me this week to check this PR, thanks!

[CarlosLanderas]

@Franklin89 could you address the merge problem in this PR? Thanks

[Franklin89]

@CarlosLanderas of course, do you have an idea for the message that should be sent to SEQ?

Currently it just shows this, but I have no Idea at the moment what the best message is for a User:

[unaizorrilla]

Hi @Franklin89

can you fix this minor issues?

[Franklin89]

@unaizorrilla I made the requested changes. Let me know if there is anything else that should be done.

[unaizorrilla]

Merged with some minor changes! Matteo, can you try to add a Seq docker image in the docker-compose in order to test this publisher?