Strip whitespace out of feature/actor/group values posted by UI

[KevinBongart]

Fix #204

By investigating the initial issue, I was able to identify several areas impacted by it.

1. Using the UI to create two features with similar names but different whitespace:

> $flipper.features
=> #<Set: {#<Flipper::Feature:70136261075520 name="   whitespace", state=:conditional, enabled_gate_names=[:actor], adapter=:memoizable>,
 #<Flipper::Feature:70136261217520 name="   whitespace   ", state=:conditional, enabled_gate_names=[:actor], adapter=:memoizable>}>

2. Still via the UI, adding an actor to the second one seemed to have actually added it to the first one.

3. Both links in the UI leads to the same feature:

4. Copy-pasting actor values from one Flipper UI to another adds some whitespace which ends up in Flipper:

> $flipper["   whitespace"].actors_value
=> #<Set: {"    [email protected]\t"}>

This PR fixes all of these issues above by applying String#strip to the params send from the front-end to the back-end of Flipper UI.

cc @jnunemaker & @AlexWheeler for review/feedback, and @susanblueapron for finding the bug in the first place

[midu]

looks like the code expects a possible nil value here, which means that your change on line 27 will raise an undefined method for nil nilclass

maybe strip inside the if block?

[midu]

same as above

[midu]

maybe add a test where you don't pass a value? seems like that's missing here

[KevinBongart]

@midu Added more tests related to empty values (not exactly the same as a param hash missing the "value" key but close enough). Not sure what's best between:

1. value = params["value"].to_s.strip
2. value = params["value"]&.strip (only compatible with Ruby 2.3+ I believe?)
3. value = params["value"] && params["value"].strip

I do wanna make sure the value (nil, empty or present) is converted to a string and cleaned up before we test for its validity so that the UI helps the user as much as possible

[jnunemaker]

My preference is to_s.strip. It works with older versions of ruby and flipper doesn't care about nil uniquely since nil/blank are treated the same.

[jnunemaker]

Looks great. Thanks!