Allow disabling user links

[metalelf0]

This commit changes the user link partial to render a span element
instead of a link when the user_path lambda is evaluated to nil.

Therefor, it allows disabling all user links by setting the user_path
lambda to always return nil.

This can be useful if, for any reason, you only want to link to some
user profiles (just write the lambda so that it returns only valid
links, and nil otherwise), or if you want to completely disable the
profile link feature.

[metalelf0]

@glebm : I suppose specs are failing because of this example I added in spec/views/thredded/user/link_spec.rb:

  it 'with nil user path' do
    Thredded.user_path = ->(_user) { nil }
    render_partial build_stubbed(:user, id: 5, name: 'joel')
    expect(rendered).to eq <<-HTML.strip_heredoc
      <span class='thredded--username'>joel</span>
    HTML
  end

This has the side effect of changing the Thredded.user_path lambda for the rest of the spec suite. I tried using the with_thredded_setting around block as used elsewhere but it's not working for this specific setting. Any hint about how I can solve this?

[glebm]

To fix the test failures, this might help:

it 'with nil user path', thredded_reset: [:@@user_path] do

If it doesn't work, try applying thredded_reset to a describe or a context block.

[metalelf0]

@glebm thanks, that worked :)

[jayroh]

ha - I didn't even know thredded_reset existed! Good to know