Enumerate the supported actors and their interactions (sequence diagrams) with the registry

[afcondon]

Creating this issue as a central place to enumerate all the possible (supported) interactions so that we can diagram them, both as documentation and to assist in understanding the aggregate properties of the system vis-a-vis complexity, coherence, explainability, totality, correctness etc.

Let's get the list first and then work on the diagrams second. Hand- or tablet-drawn diagrams would be fine, i guess. If its of any interest, i've had this open in a tab for a long time and have never tried it, but i like the idea of a markdown like syntax that we can capture easily here in issues, and i think GraphViz doesn't do Sequence Diagrams natively.

[afcondon]

Some of the actors that i've observed being discussed so far:

1. package owner, add previously existing package to registry
2. package owner, new package
3. (person submitting package for which they are not owner), existing package
4. (person submitting package for which they are not owner), new package

this is just illustrative, i'm not entirely clear what the list is

quite possible that it's best to create a table / spreadsheet first rather than a list if there are a LOT of combinations

[f-f]

I'll mention #84 and #85 that are about graphing some interactions. Not sure if these issues should all be merged into one?