Feature: add a new `diff` subcommand

[strangemonad]

The semantics I'd imagine for this is to closely mirror the kubectl diff behavior. The use case would be to pair dash0 diff with dash0 apply --dry-run and dash0 apply.

This would be even better if there were a apply --dry-run --server-side variant of dry-run.

[mmanciop]

We have diff output on apply, including on dry runs: https://github.com/dash0hq/dash0-cli/blob/main/docs/commands.md#apply

I am not understanding the functional gap.

[strangemonad]

@mmanciop I've not been able to successfully use apply at all for dashboards or views.

A) local file with no uuid, apply uses the create path, creates a new server resource but

1. returns no information about the uuid of the created dashboard to be able to update the local file
2. strips any permission from the local file
3. metadata.dash0Extension.id doesn't match the server uuid id
4. the createdBy uses an oauth aud key e.g. user_2tH... but all other endpoints to query users return user uuids

❯ dash0 apply -f  assets/apps/app/dashboards/dash0-vercel-project-activity.dashboard.yaml
Dashboard "Dash0 - Vercel Project Activity" (api-9b430f70-f581-4927-9b4a-039be7a65b57) created

infra/observability/dash0  shawn/dash0-assets-baseline*​ ≡
❯ dash0 dashboards list|grep Vercel
Dash0 - Vercel Project Activity           2a1b7fed-f9f5-4205-88cf-206e6ce16081
Dash0 - Vercel Project Activity           6ddef905-5fa7-4937-bb15-f8d700734d58
Dash0 - Vercel Project Activity           c3c06945-8337-4db9-b4a7-c49782487081

B) local file with a uuid but doesn't exist yet. First call creates it (still strips permissions), second call responds with "no updates" but it seems to actually still run through the update path and blow away my current user's permissions to edit the asset. Third call fails with 404

eg with a new view

infra/observability/dash0  shawn/dash0-assets-baseline*​ ≡3s
❯ dash0 apply -f  assets/apps/admin-streamlit/views/service-admin.view.yaml
View "Service admin" (48f9928f-68d8-4c45-8609-a7f1d83aafff) created

infra/observability/dash0  shawn/dash0-assets-baseline*​ ≡
❯ dash0 apply -f  assets/apps/admin-streamlit/views/service-admin.view.yaml
--- View (before)
+++ View (after)
@@ -16,11 +16,6 @@
   - otel.log.severity.range
   implicitFilter: []
   permissions:
-  - actions:
-    - views:read
-    - views:write
-    - views:delete
-    userId: 14843e48-4d19-4126-81b6-005a5eb1f18a
   - actions:
     - views:read
     - views:delete

infra/observability/dash0  shawn/dash0-assets-baseline*​ ≡
❯ dash0 apply -f  assets/apps/admin-streamlit/views/service-admin.view.yaml
Error: document 1 (Dash0View): view "service-admin" not found (status: 404, trace_id: f5e83a5bddd9ac61d2f9d52825019ac9):
  Not Found: The requested view does not exist or is inaccessible to you.
Hint: run `dash0 skill install` to add a local Agent Skills bundle with detailed command references

eg with an existing dashboard

infra/observability/dash0  shawn/dash0-assets-baseline*​ ≡
❯ dash0 apply -f  assets/apps/app/dashboards/dash0-vercel-project-activity.dashboard.yaml
Dashboard "Dash0 - Vercel Project Activity": no changes

infra/observability/dash0  shawn/dash0-assets-baseline*​ ≡
❯ dash0 apply -f  assets/apps/app/dashboards/dash0-vercel-project-activity.dashboard.yaml
Error: document 1 (Dashboard): dashboard "Dash0 - Vercel Project Activity" not found (status: 404, trace_id: a1b3af8dd4d4f77eaf3990ac9b160713):
  Not Found: The requested dashboard does not exist or is inaccessible to you.
Hint: run `dash0 skill install` to add a local Agent Skills bundle with detailed command references