invalid .$sample_id-replacement currently passes with a warning

[HelenaLC]

Issue

In previous versions, the colData-replacement method assured that replacing the sample_id column in colData only passed provided that

1. old and new IDs have a one-to-one mapping
2. the number of unique IDs is retained
3. IDs aren't set to NULL

Currently, breaking any of these gives a warning(), but the replacement is carried out regardless. As a result, entries in imgData are no-longer mappable to the cells, since sample IDs can be removed, arbitrarily reordered, or overwritten with a different number unique IDs.

Proposal

Revert to the previous replacement implementation, which

1. stop()s invalid replacement
2. passes replacement with NULL but retains sample_ids

[HelenaLC]

Current plan from meeting:

• replace warning()s with stop()s
• give extra informative warnings, including pointers to documentation
• add documentation on colData-replacement in colData<-, SpatialExperiment and vignette

(assigned @lmweber to cover documentation, including some examples of invalid/valid replacements, and demonstrating how to cbind e.g. 2 experiments each with section1/2 as sample IDs; the rest is still open)

[HelenaLC]

fixed via #50