label_column option in metadata.json

[simonw]

Currently the column used for displaying a foreign key relationship is automatically detected by inspect() by looking for tables that have a primary key column and one other column.

This doesn't work for tables with more than two columns.

Let's allow the table section in metadata.json to optionally define a label_column which, if present, will be used for those displays.

[simonw]

    "databases": {
        "database1": {
            "tables": {
                "example_table": {
                    "label_column": "name"
                }
            }
        }
    }
}

[simonw]

Docs here: http://datasette.readthedocs.io/en/latest/metadata.html#specifying-the-label-column-for-a-table

[simonw]

I built this wrong: my implementation is looking for the label_column on the table-being-displayed, but it should be looking for it on the table-the-foreign-key-links-to.