Append to existing apps.json preload state instead of overwriting

[alexgg]

This is to remain in draft state until the v3 target state API changes are merged

---

If the image we are preloading to contains an existing apps.json append the preloaded app to it instead of overwriting it.

Fixes balena-io/balena-cli#2262

Relates to balena-io/balena-cli#2263

Change-type: patch Signed-off-by: Alex Gonzalez alexg@balena.io

---

Tested on a raspberrypi4-64-2.75.0+rev1 image that does not contain a preloaded apps.json, and on a genericx86-64-ext development build with an existing apps.json with preloaded state.

[alexgg]

Validation on a devenv with a draft v3 state endpoint:

[x] Preloading on an image with preloaded apps.json with a v3 state supervisor

• v3 style app is appended to apps.json [x] Preloading on an image with preloaded apps.json with a v2 state supervisor (should not happen) Fails with:

  The preloaded app state and the current state in the image have a version mismatch. Please use afresh, not previously preloaded image file

  [x] Preloading on an image without apps.json with a v2 state supervisor

• v2 stype app appears in apps.json [x] Preloading on an image without apps.json with a v3 state supervisor (should not happen)
  • v3 state app appears in apps.json