getIPWeights - need to add a check that user has specified PS model for all nodes on which we intervene

[romainkp]

Say user specifies stratified PS models for A (resp. C or N) nodes such that the union of the person-time observations on A that fall in each stratum is not equal to the total number of person-time observations in the dataset.

Say that the user then asks stremr to compute an effect estimate for interventions on a subset of the A nodes (resp. C or N) such some elements of the subsets of person-time observations on A do not fall into any of the strata specified for gA.

Stremr should then return an error message to warn the user than they did not specify a sufficient number of strata for gA. Currently, stremr will return an output which will be incorrect.

Idea to fix this: add an argument check in getIPWeights that checks that the A (resp. C and N) person-time observations on which the user wish to intervene are all contained in the union of the person-time observations on A that fall within each stratum specified for gA. If not, stremr should give an error that asks the user to modify/add how they specified the strata for the PS model for gA.