Helper to identify the dimension of each step in aggsequence

Usage

identify_dimension(aggsequence, causal_edges)

aggsequence: a named list of aggregation steps in the order to apply them. Entries for theme aggregation should be character vectors- e.g. name = c('from_theme', 'to_theme'). Entries for spatial aggregation should be the sf polygon to aggregate to, e.g. name = sfpolygons or a length-1 character, e.g. name = "sfpolygons". The latter requires the object to be available with get("sfpolygons"), but allows passing characters rather than objects. Not requiring names and is high on the list of improvements. If we want to be able to re-run from auto-saved metadata params, we need the names of the spatial levels to match the object, e.g. basin: basin.
causal_edges: causal links between all theme levels included in aggsequence, though can also include others, which are ignored. Creates the theme grouping

character vector with 'spatial', 'theme' or 'temporal' for each step in aggsequence