update input group addon changes from bootstrap beta 3

[toadkicker]

This addresses changes introduced in twbs/bootstrap#25020

• drops the .input-group-addon class and replaces it with .input-group-prepend and .input-group-append depending on the value of the slot
• deprecates the .input-group-btn class and uses the classes above
• defaults component to input-group-append if no slot value provided
• updates specs

[codecov]

Codecov Report

Merging #1505 into dev will not change coverage.
The diff coverage is n/a.

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##              dev    #1505   +/-   ##
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  Coverage   53.26%   53.26%           
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  Files         134      134           
  Lines        2191     2191           
  Branches      698      698           
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  Hits         1167     1167           
  Misses        728      728           
  Partials      296      296

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[toadkicker]

I don't know if this should just become two separate components instead of using a slot/prop definition, e.g <input-group-prepend> vs current method. If that is preferred over this solution I'm happy to provide it.

[pi0]

Thanks. I think this change was necessary to provide this update with minimum code change impact. But adding support for <input-group-append|prepend> would be much better for long-term. So PR welcomes for those components.

[tmorehouse]

Yeah, this needs to be two new components (replacing the single add-on component and button addon).

See the issue that we are using to track the changes needed for bootstrap v4.beta.3 #1408

[toadkicker]

I got a chance to check this out more today. The new style needs to have a child element of div.input-group-text in order for the styles to get picked up. This change does not insert the additional div around the text. I'll figure out how to do that next.