New options for setting blueprint: "force", "load if unset", "set default"

[jleibs]

Builds on top of:

• Don't activate blueprint until the entire file has been received #5297

Now that a blueprint can be set at any time, we want some minimal control for the SDK for how this behaves.

Force and load-if-unset are mostly trivial and could likely be added to the "ActivateBlueprint" message proposed in (#5297)

"Set default" includes some extensions to the StoreHub.

• The basic idea is that the store-hub will store two blueprints per app-id. One is the currently active blueprint, where all user edits are applied. The other is our first implementation of a "snapshot" as the MVP of a single "default" snapshot per blueprint.

A blueprint sent from the SDK will have the option to only replace the "default" snapshot, and a new variant of the "Reset blueprint" action will be to reset to the blueprint to the (SDK-provided) default as opposed to the (Heuristic provided) default.

Consideration

If putting this data in the "ActivateBlueprint" message, we should be careful about whether that message is baked into the stream or not when saving a blueprint. If a user is opening a blueprint from file it might be weird for the file being opened to make the determination as to if the behavior is force / load if unset/ or set default.

[emilk]

Very related to

• Locally edited blueprint overridden when loading an example #5629

[jleibs]

Proposal for 0.15: Always use "load if unset + set default"

It's 1 click for a user to reset.

[jleibs]

Considering this done as of: #5678