Implement an enabled flag for all filters

[dblock]

See https://github.com/Waffle/waffle/issues/638#issuecomment-402899320

Allow all filters to be disabled with enabled='false'.

Deprecate the disableSSO option that shipped in 1.9.1 via #636.

[pedroneil]

Is the enable=false for all filters including Spring and Apache Shiro etc or is this also for a Filter Provider? e.g. the NegotiateFilterProvider would support NTLM if it is enabled, or will it be easy and stay at Filter level?

[dblock]

I mean it should be possible to do it for each individual filter, but the implementation should be shared.

[hazendaz]

@dblock What was your originally thinking on why to switch "Naming wise, I would change disableSSO to enabled"? I got away on other things back in 2018 when that was originally added. It was only recently I started to use some of the newer logic, not this flag exactly but the abiilty for this to always run on windows and for a vintela filter to run on linux. In my case I made both live. That part seemed a bit contensious as well at the time but for cross platform it works beautifully now. So I think based on tickets I'm seeing that there was a left over concern to switch 'disableSSO' to 'enabled'. I do agree that reads better but give the going on 2 year gap I'm not sure if that still makes sense to really do or not. I also have no real insight into how many are actually using the parameter that was added. What I do know is that vintela I if I recall came with a very similar option in naming around disableVsj or something to that effect.

[dblock]

Yes, I only was commenting on the naming.