Add support for basic auth in couchdb input

[danielnelson]

closes: #5155

Required for all PRs:

• Signed CLA.
• Associated README.md updated.
• Has appropriate unit tests.

[danielnelson]

@fungiboletus I added support for basic auth to the couchdb plugin, but have not tested it on a real server. Do you think you would be able to test it out with one of these builds? (let me know if your build is not listed here)

• telegraf-1.10.0%7E613ed17e-0.x86_64.rpm
• telegraf_1.10.0%7E613ed17e-0_amd64.deb
• telegraf-1.10.0%7E613ed17e_windows_amd64.zip

[glinton]

I probably would have just called it Username/Password to stay uniform with other plugins (elasticsearch, kibana, icinga2, rabbitmq, etc...)

[danielnelson]

I was on the fence about this but decided to be more explicit because CouchDB supports several authentication methods. We have a number plugins using this naming as well and I could go either way.

I would probably never consider implementing the cookie method, but the proxy method is a possibility. I guess if we added it we could provide another option auth_method? Which way do you think is best?

[glinton]

Sound logic. I say leave it, as you said, there are other plugins that use the basic_ prefix.

[fungiboletus]

@danielnelson Thanks, that was fast. I tested it and it worked as expected.

[nbari]

I am getting this error:

E! [telegraf] Error running agent: Error parsing telegraf.conf, line 29: field corresponding to `basic_username' is not defined in `*couchdb.CouchDB'

The configuration I am using is for couchdb2

[[inputs.couchdb]]
  hosts = ["http://127.0.0.1:5984/_node/_local/_stats"]
  basic_username = "foo"
  basic_password = "bar"

[danielnelson]

@nbari What version of Telegraf do you have, it will need to be 1.10.0.

[nbari]

I am using 1.9.3, will try updating to 1.10.0