default MOTD

[johrstrom]

It came up today that maybe we should have a default message of the day to something like below.

Development of Open OnDemand is supported through the [National Science Foundation](https://www.nsf.gov/) 
under grant numbers [1534949](https://www.nsf.gov/awardsearch/showAward?AWD_ID=1534949) and 
[1835725](https://www.nsf.gov/awardsearch/showAward?AWD_ID=1835725).

While we're at it, maybe we'd also add notes on Discourse, this GH repo and our documentation website as well.

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[ericfranz]

It came up today that maybe we should have a default message of the day

What is the source of this?

If we want a reference to the NSF grants we should fix that somewhere appropriate. We might consider another widget in place of the MOTD. I'm not sure about a default MOTD.

[johrstrom]

Bob and Alan mentioned it in our OnDemand slack channel.

[johrstrom]

A comment I had from #913 I think is a good strategy for how to do this:

The tests are a reminder that there should be some way to disable this too. Like, by default we have this MOTD, but if you set MOTH_PATH="" or similar as a way to disable it (I'm not sure what the failing tests initialize, but they can set this empty here).

It'd probably be best to use a motd_default type and just inheret from the markdown so we can drop the default in the views directory itself and get rid of that ugly nested if block.

# app/models/motd_formatter_default.rb
class MotdFormatterDefault < MotdFormatterMarkdown

  def to_partial_path
    "dashboard/motd_default"
  end
end

[matt257]

reviewed, add a link for ood-core repository, reference important gems, discourse, OOD staff section