[Fleet] Add agent input template for the fleet server package

[nchaulet]

Description

Resolve #803

Currently we do not send the config from kibana to fleet server as there is not input agent template, we should add one.

This PR fix that by adding an agent template for the fleet server input, I also added the field max_connections introduced here elastic/fleet-server#153

Agent policy with the template

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[elasticmachine]

💚 Build Succeeded

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Build Cause: Pull request #806 updated

• Start Time: 2021-03-26T12:56:53.823+0000

• Duration: 12 min 48 sec

• Commit: 4ba359b

Trends 🧪

[ruflin]

I tested this and got the following:

    data_stream:
      namespace: default
    server:
      port: 8220
      host: 0.0.0.0
      max_connections: '12'

I wonder why it treats port as an int but max_connections it doesn't?

[nchaulet]

Good catch the port was correct because it was using the default value, but both variable types where incorrect I just changed them from text to integer and it's working

[ruflin]

LGTM. Policy looks as following:

  - id: 3f0744e7-076c-4a6d-94c7-5a961e50dcf7
    name: fleet_server-1
    revision: 2
    type: fleet-server
    use_output: default
    meta:
      package:
        name: fleet_server
        version: 0.2.0
    data_stream:
      namespace: default
    server:
      max_connections: 45
      port: 8220
      host: 0.0.0.0

I assume the data_stream part is just filled in by Kibana, at one stage we should probably remove this.

[ruflin]

One thing I noticed is that i can put any value into integers fields like foo and it accepts it. Not directly related to this PR but probably worth to follow up on.