This is the implementation of the new DB connections API (grant proposal 2019).
Summary
The new API makes it available to QGIS core a new interface for provider connections and will allow to:
replace the provider specific QgsSettings management in QGIS4 (save/load connections from the settings) NOT IN SCOPE FOR NOW.
provide a unified API for common operations on DB connections:
executeSql and get the results
list tables names and properties and schemas
create a new vector table (no rasters for now)
create/rename/drop schemas and tables
vacuum
....
- grass data item provider fixes
- removed QgsProviderMetadata constructor (with std::function / PyObject) due to sip errors (api break)
- reverted DataCapability move to Qgis - back to QgsDataProvider (avoiding api breaks)
- WidgetMode enum documentation
- sipify monkey patching fix
- renamed WidgetMode's "None" to "Normal" value - in python None has special meaning (api break)
For the c++ api dox this expands to "\c nullptr" (the
\c directive indicates a code literal value), and for sipify/Python
it expands to ``None`` (`` is sphinx annotation for literal values)
Makes for nicer dox for both c++ and Python!
