Allow custom functions

[huaxk]

Just change const functions to a compile-time sequence variable , you can implement custom function. so can write code:

static:
  functions.add([
    Function(name: "st_asgeojson", arity: 1, typ: dbVarchar),
    Function(name: "json", arity: 1, typ: dbJson),
  ])

let cities = query:
  select cities(id, name, st_asgeomjson(lnglat))

echo cities

It is possible to take advantage of databse built-in function.

[Araq]

Ok, can you add a test case for this please?

[huaxk]

It involves database operations, and need to set up a CI system based on github actions. I can try!

[Araq]

Please remove the tests/tpostgres binary file.

[huaxk]

I set up automated tests base on github actions, and tested crud, may be some problems with the delete operation, it raise unhandled exception. I test some sql function: upper and lower, which functions with only one parameter works ok! but others has problems.

[Araq]

Does that mean you want me to review it? Or is this "work in progress"?

[huaxk]

Yes, The automated tests has been set up. After you reviewed, then I can test more cases and fix the bug I found.

[huaxk]

The current test is mainly for postgresql, and the next step can also be for sqlite.

[Araq]

Looks good enough to me.