Create a GRG that takes input breaklines into account

[BobBooth]

As a user I need to create a GRG that takes existing natural break lines into account. User should be able to upload a set of features that should split any polygons generated by the GRG tool. For example, major rivers, main highways, ridge lines.
Tool should allow for a minimum polygons size to be set to avoid "splinter" polygons. Splinters to be dissolved into an adjacent poly (but shouldn't be dissolved across a break line).
Tool should warn when too many features are uploaded. E.g. someone submits the Redlands streets network as breaks. Tool should say this is too many - select the most important lines (major roads, highways) and try again.

After processing, results should be interactively adjustable before publish.
Should get preliminary numbers, but the user should have a set of tools to adjust the data, to include:
a) Merge tool - click a segment and it disappears, the polygons on either side merge.
b) Split tool - sketch a line across a polygon to split it.
c) Undo tool - reverses last action.
d) renumber - after geometries adjusted, user should be able to trigger a renumber of the polygons.

Screenshots

Related to:
#126
#1

[adgiles]

I feel we are in trouble of trying to replicate desktop GIS functionality into a browser here. There are also analysis tools within the platform that do some of these requirements:

https://doc.arcgis.com/en/arcgis-online/analyze/overlay-layers.htm