.check_portfolio overwrites assetid if present

[goergen95]

The value of assetid is currently overwritten if it is present:

mapme.biodiversity/R/portfolio.R

Lines 216 to 223 in 872cbd6

	if ("assetid" %in% names(x) && verbose) {
	msg <- paste("Found a column named 'assetid'.",
	"Overwritting its values with a unique identifier.",
	sep = " "
	)
	message(msg)
	}
	x[["assetid"]] <- 1:nrow(x)

However, to support advanced use cases (e.g. batching and chunking), it would be better if we check for uniqueness of its value and only overwrite if assets are not uniquely identified.