[MM-14720] Add Posts Per Day Analytics and Number Posts Previous Day Functionality (#11402)

* Add ability to get bot counts per day

Modify tests using AnalyticsPostCountsByDay to include extra input
(botsOnly)

Correctly generate the mock file with 'make store-mocks' target.  Didn't
see these comments earlier

* Initial commit for calculating total posts previous day and total posts
from bots previous day

* - Refactor to use asserts instead of if statements in tests
- Capture inputs to AnalyticsPostCountsByDay() function into an
  options struct
- Remove bot creation from diagnostics_test.go.

* Remove utils library

* create AnalyticsPostCountsOptions struct which is accepted as an input
to AnalyticsPostCountsByDay method

* Go vet fixes

app/diagnostics.go

@@ -134,6 +134,8 @@ func (a *App) trackActivity() {
 	var deletedPublicChannelCount int64
 	var deletedPrivateChannelCount int64
 	var postsCount int64
+	var postsCountPreviousDay int64
+	var botPostsCountPreviousDay int64
 	var slashCommandsCount int64
 	var incomingWebhooksCount int64
 	var outgoingWebhooksCount int64
@@ -188,6 +190,20 @@ func (a *App) trackActivity() {
 
 	postsCount, _ = a.Srv.Store.Post().AnalyticsPostCount("", false, false)
 
+	postCountsOptions := &model.AnalyticsPostCountsOptions{TeamId: "", BotsOnly: false, YesterdayOnly: true}
+	postCountsYesterday, _ := a.Srv.Store.Post().AnalyticsPostCountsByDay(postCountsOptions)
+	postsCountPreviousDay = 0
+	if len(postCountsYesterday) > 0 {
+		postsCountPreviousDay = int64(postCountsYesterday[0].Value)
+	}
+
+	postCountsOptions = &model.AnalyticsPostCountsOptions{TeamId: "", BotsOnly: true, YesterdayOnly: true}
+	botPostCountsYesterday, _ := a.Srv.Store.Post().AnalyticsPostCountsByDay(postCountsOptions)
+	botPostsCountPreviousDay = 0
+	if len(botPostCountsYesterday) > 0 {
+		botPostsCountPreviousDay = int64(botPostCountsYesterday[0].Value)
+	}
+
 	slashCommandsCount, _ = a.Srv.Store.Command().AnalyticsCommandCount("")
 
 	if c, err := a.Srv.Store.Webhook().AnalyticsIncomingCount(""); err == nil {
@@ -208,6 +224,8 @@ func (a *App) trackActivity() {
 		"direct_message_channels":      directChannelCount,
 		"public_channels_deleted":      deletedPublicChannelCount,
 		"private_channels_deleted":     deletedPrivateChannelCount,
+		"posts_previous_day":           postsCountPreviousDay,
+		"bot_posts_previous_day":       botPostsCountPreviousDay,
 		"posts":                        postsCount,
 		"slash_commands":               slashCommandsCount,
 		"incoming_webhooks":            incomingWebhooksCount,