Fixes#1148
This PR adds expressway tagging to the `transportation` layer, by setting `expressway=1` for non-motorway roads tagged `expressway=yes`, and omitting the tag otherwise. Additionally, I've added a few unit tests to verify that the expressway tagging is being imported and updated into the intermediate tables.
Here is an example of expressway tagging on US-1 in Rhode Island, USA:
I discovered this bug while investigating issues with the updates process related to #1190#1292, and #814.
The `transportation_name` layer produces slightly different `tags` hstore values in the `osm_transportation_name_linestring` table during the initial import versus when running an update. As currently written, the import code produces null-value keys in the `tags` column, while the update code suppresses them. This PR removes that difference and makes the import code use same method that is currently used in the update code.
With a test case I've written, the import code produces a tags hstore that looks like this:
`"name"=>"OpenMapTiles Secondary 2", "name:de"=>NULL, "name:en"=>NULL, "name_int"=>"OpenMapTiles Secondary 2", "name:latin"=>"OpenMapTiles Secondary 2"`
...while the update code produces a tags hstore that looks like this:
`"name"=>"OpenMapTiles Secondary 2", "name_int"=>"OpenMapTiles Secondary 2", "name:latin"=>"OpenMapTiles Secondary 2"`
Note the missing NULL values.
This bug causes a small amount of space wastage after an update is run, because the update matching code detects the `tags` value as different, resulting in a duplicate copy of the tags value if that row is updated. This causes duplicate objects and breaks GROUP BY clauses that expect to group same-tagged features together. I've tested this by inspection of a generated mbtiles, database spot checks, and the unit test code included in this PR.
This PR adds unit tests for the transportation layer, and fixes several bugs in the unit testing code. It verifies the correct zoom association to the various highway classes, and verifies that updates to highway attributes are populated.
Additionally, the documentation for unit tests in the CONTRIB guide is updated to note the specific make commands for developers to run.
Brian Sperlongano
