When expressions are generated with SQLAlchemy, any constants are
replaced with bind parameters. The bind parameters become parameters of
prepared statements. The result is that the query planner tends to
oversee that the partial indexes can be used.
Search is now split into three functions: for free-text search,
for structured search and for search by category. Note that the
free-text search does not have as many hidden features like
coordinate search. Use the search parameters for that.
This switches the input parameters for API calls to a generic
keyword argument catch-all which is then loaded into a dataclass
where the parameters are checked and forwarded to internal
function.
The dataclass gives more flexibility with the parameters and makes
it easier to reuse common parameters for the different API calls.
The only allowable difference is precision of coordinates. Python uses
a precision of 7 digits where possible, which corresponds to the
precision of OSM data.
Also fixes some smaller bugs found by the BDD tests.
The implementation follows for most part the PHP code but introduces an
additional layer parameter with which the kind of places to be returned
can be restricted. This replaces the hard-coded exclusion lists.
