refactor maps merging in RepositoryEnricher

[vincent-fuchs]

Summary

we can do better than

github-crawler/github-crawler-core/src/main/kotlin/com/societegenerale/githubcrawler/RepositoryEnricher.kt

Lines 128 to 145 in 572c25f

	//TODO rewrite this in a functional Kotlin way, to reduce maps
	miscRepositoryTasks.forEach{
	val miscRepoTaskResult=it.perform(repo)
	for ((branch, value) in miscRepoTaskResult) {
	if(resultsCollector[branch]==null){
	resultsCollector[branch]=value
	}
	else{
	val existingValuesForBranch=resultsCollector[branch]!!.toMutableMap()
	existingValuesForBranch.putAll(value)
	resultsCollector[branch]=existingValuesForBranch
	}
	}
	}

--> let's refactor it, leveraging on Kotlin features. Unit test is already in place to validate we don't break anything

Type of Issue

It is a :

• request