refactor: implement warnings as notices

[benhoyt]

This deletes the legacy warnings code and re-implements pebble warnings and pebble okay using notices as warnings (as we originally intended). The /v1/warnings endpoints have been removed, and pebble warnings now hits /v1/notices?types=warning.

On every request, instead of returning the count of warnings and the latest timestamp, we only return the timestamp of the latest (most recent last-repeated time). This way the server doesn't have to track which notices have been okayed -- the client can compare against its stored timestamp and see if the server-reported timestamp is later.

So there are a few breaking changes in this PR:

• Client.WarningsSummary() (count int, timestamp time.Time) is now Client.LatestWarningTime() time.Time, as there's no count anymore
• GET /v1/warnings (list warnings) is gone: pebble warnings now uses GET /v1/notices?types=warning
• POST /v1/warnings (okay warnings) are gone: pebble okay now just updates the local state file, and doesn't use the API/client at all
• Similarly, Client.Warnings() and Client.Okay() are gone; use Client.Notices() and maintain local client-side state, respectively
• State.Warnf is still around, but it's now just a helper that calls State.AddNotice with the right type (warning) and key (message)

Currently Pebble itself doesn't record any warnings, so you can't test easily without making a code change. To perform manual tests, I hacked the API endpoint used by pebble notify to record warning notices instead of custom ones:

diff --git a/internals/daemon/api_notices.go b/internals/daemon/api_notices.go
index 8cd2745..7b62f19 100644
--- a/internals/daemon/api_notices.go
+++ b/internals/daemon/api_notices.go
@@ -201,9 +201,9 @@ func v1PostNotices(c *Command, r *http.Request, user *UserState) Response {
        if payload.Type != "custom" {
                return BadRequest(`invalid type %q (can only add "custom" notices)`, payload.Type)
        }
-       if !customKeyRegexp.MatchString(payload.Key) {
-               return BadRequest(`invalid key %q (must be in "example.com/path" format)`, payload.Key)
-       }
+       //if !customKeyRegexp.MatchString(payload.Key) {
+       //      return BadRequest(`invalid key %q (must be in "example.com/path" format)`, payload.Key)
+       //}
        if len(payload.Key) > maxNoticeKeyLength {
                return BadRequest("key must be %d bytes or less", maxNoticeKeyLength)
        }
@@ -228,7 +228,7 @@ func v1PostNotices(c *Command, r *http.Request, user *UserState) Response {
        st.Lock()
        defer st.Unlock()
 
-       noticeId, err := st.AddNotice(user.UID, state.CustomNotice, payload.Key, &state.AddNoticeOptions{
+       noticeId, err := st.AddNotice(nil, state.WarningNotice, payload.Key, &state.AddNoticeOptions{
                Data:        data,
                RepeatAfter: repeatAfter,
        })

Fixes #475.

[hpidcock]

LGTM. A few comments. Looking forward to the follow-up review that removes the mutex lock on the daemon response code for warnings.

[hpidcock]

Are you going to follow up with this PR soon? It seems like then we can finally get rid of the mutex lock in the daemon response code.

[benhoyt]

Yes, it's my plan to do a follow-up PR shortly after this one.

[hpidcock]

This would seem to only panic when the message is an empty string. That seems OK.

[hpidcock]

I think, at some point, we need to improve saveCLIState to atomically write the state file (and to include conflict resolution).

[hpidcock]

Nice detail.

[IronCore864]

Some questions/comments on this feature in general after testing: