add validation to argocd app set -p

[JazminElkan-Gonzalez]

This fixes #195

I rebased to clean up commit history but change was contributed by @dthomson25

Util function checks if a given parameter matches component and name to a parameter in the given application.

server side "updateSpec" function uses util to verify passed override parameters along with all previous override parameters.

client side "app set" function also uses util to verify passed override parameter before calling "updateSpec"

throws error if passed parameter is illegal, warns users if any old overrides are dropped

[dthomson25]

Do we want to extract this into the Utils since it's the same code on server and cli?

[JazminElkan-Gonzalez]

if we put this into CheckValidParam than we have to loop through it for every parameter, I put it here so we would only have to loop through it once per UpdateSpec. rather than once per parameter.

I could make a Util that is "convertToMap" that does the loop as a separate function.

[jessesuen]

1. The error check that used to come immediately after the Applications().Get() request, now comes after this large code block. So its possible to get a nil pointer exception while you are attempting to validate the params (a might be nil).

2. I think this validation logic is large enough that it should be put into a separate function to keep the UpdateSpec more concise.

[JazminElkan-Gonzalez]

1. ah good point will reorder.
2. ok, makes sense will create a helper function tomorrow.

thanks for the feedback!

[jessesuen]

I don't see the need to do this client side validation if we are already doing this server side

[JazminElkan-Gonzalez]

mm the thought was to have it fail fast (before it even gets to the server side logic). but given that it's a relatively costly process / to keep things clean, I think it makes sense to omit this.

[JazminElkan-Gonzalez]

@jessesuen I made the changes we spoke about, here is some example outputs.

[jessesuen]

LGTM! please squash commits when merging