Handle string credentials #834

Job	Run time
spec (ruby 2.7 \| puppet ~> 7.0) / spec	1m 41s
spec (ruby 3.2 \| puppet ~> 8.0) / spec	1m 28s
acceptance (windows-latest ruby 3.2 \| puppet ~> 8.0) / acceptance	8m 53s
acceptance (windows-latest ruby 2.7 \| puppet ~> 7.0) / acceptance	9m 38s
	21m 40s

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