Correlations tab: assay used for feature choice is not necessarily the RNA assay

[wish1832]

The correlation tab currently only shows features from the first assay as selectable choices. This is fine in our Seurat Objects when gene is always the first assay, but it could cause problems when other objects are loaded. This could be fixed by changing the choices argument below to depend on either a designated gene assay from the config file, or a list of assays enabled for correlations in the config app (though this would raise the issue of how best to run correlation analysis with multiple assays).

updateSelectizeInput(
                       session,
                       inputId = "feature_selection",
                       choices = valid_features()[[1]],
                       selected = character(0),
                       server = TRUE
                       )

[wish1832]

This needs to be corrected before public release, or it could render the correlations tab unusable on other users' datasets.

[wish1832]

This also needs to be done for the DGE tab. Presto tests whichever assay is the default assay, but this may not necessarily be genes.

[wish1832]

As of the most recent version on main, the DGE tab and the correlations tab will use the designated genes assay in the config app, or the first assay if this is undefined.