initAlgorithm() method
This allows 2 benefits:
- algorithms can be subclassed and have subclasses add additional
parameters/outputs to the algorithm. With the previous approach
of declaring parameters/outputs in the constructor, it's not
possible to call virtual methods to add additional parameters/
outputs (since you can't call virtual methods from a constructor).
- initAlgorithm takes a variant map argument, allowing the algorithm
to dynamically adjust its declared parameters and outputs according
to this configuration map. This potentially allows model algorithms which
can be configured to have variable numbers of parameters and
outputs at run time. E.g. a "router" algorithm which directs
features to one of any number of output sinks depending on some
user configured criteria.
Nothing particularly exciting here yet, but this commit
moves the definition of the provider base class to a c++
QgsProcessingProvider abstract base class.
As part of this some existing python methods were renamed
to make their use clearer and to fit with the QGIS c++
api conventions:
- getName was renamed to id
- getDescription was renamed to name
- getIcon was renamed to icon
These API breaks are documented
