fix: applyCssClass value initialization

[salarenko]

Please provide a link to the associated issue.

Closes: #3181

Please provide a brief summary of this pull request.

This PR brings:

• Proper initialization of _classMap[this._uuidv4] value, previously initialized with nested array instead of an array
• Proper typing for updateComponentClassList(..., previousComponentClassList,..) argument

Please check whether the PR fulfills the following requirements

• the commit message follows the guideline:
  https://github.com/SAP/fundamental-ngx/blob/master/CONTRIBUTING.md
• tests for the changes that have been done
• all items on the PR Review Checklist are addressed :
  https://github.com/SAP/fundamental-ngx/wiki/PR-Review-Checklist

Documentation checklist:

• update README.md
• Breaking Changes Wiki
• Documentation Examples
• Stackblitz works for all examples

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[dimamarksman]

would be good to add proper typing for firstCommonElementIndex as well

fundamental-ngx/libs/core/src/lib/utils/decorators/apply-css-class.decorator.ts

Line 51 in e95e4a5

function firstCommonElementIndex(array1: string[], array2): number {

[dimamarksman]

Looking at function signature and naming:

fundamental-ngx/libs/core/src/lib/utils/decorators/apply-css-class.decorator.ts

Lines 51 to 54 in e95e4a5

	function firstCommonElementIndex(array1: string[], array2): number {
	const index = array2.findIndex(element => array1.indexOf(element) !== -1);
	return index === -1 ? 0 : index;
	}

There are some things in this function that are not clear for me:

• Why we try to find index in the second array and not first
• Should this function be responsible for rounding index === -1 ? 0 : index

[salarenko]

@dimamarksman

• added argument typing for firstCommonElementIndex
• I had similar concenrs to index "rounding", moved out of the function
• you are right this should be arr1.(arr2) not arr2.(arr1)

I also added some logic to split multiple classes merged into one string
(['class1', 'class2 class3', 'class4'] => ['class1', 'class2', 'class3', 'class4'])

[InnaAtanasova]

@dimamarksman let us know if you think the PR is ok (I'm not sure if you can approve it :) If you can, please approve)

[InnaAtanasova]

LGTM

[dimamarksman]

LGTM,
I'm not able to approve.