[v9.5.x] SQL Datasources: Update Max Connection and Max Idle Connection Defaults to 100 and add auto mode (#66651)

* SQL Datasources: Update Max Connection and Max Idle Connection Defaults to 100 and add auto mode (#65834)

* Update connection configuration for SQL datasources

* Working auto state for connection numbers

* Add migration

* Use defaults from constants file

* Remove dead code

* Add tests and restructure useMigrateDatabaseField

* Update function names

* Update docs

* Make sure we don't continually issue updates

* Update docs

* Use onOptionsChnage in ConnectionLimits

* Update docs

* Clean up docs

* Update migration

* Fix default values in docs

* Fix spacing issue

* Fix test

* Update default values for SQL connections

* Include consts

* Allow override for default SQL datasource connection parameters

* Fix linter errors

* Remove extra @ts-ignore

* Centralize logic for default values

* Remove debugging

* Remove unecessary function

* Update configuration docs

* minor suggested change

* Fix comment misspelling

* Remove unecessary default setting code

* Update docs to indicate that code was included for backport version

* Remove dead code

---------

Co-authored-by: lwandz13 <larissa.wandzura@grafana.com>
(cherry picked from commit 92d92187d9)

* Add brackets around property name so that it's dynamic

---------

Co-authored-by: Kyle Cunningham <codeincarnate@users.noreply.github.com>
Co-authored-by: Kyle Cunningham <kyle@codeincarnate.com>

pkg/setting/setting.go

@@ -369,6 +369,11 @@ type Cfg struct {
 	// Data sources
 	DataSourceLimit int
 
+	// SQL Data sources
+	SqlDatasourceMaxOpenConnsDefault    int
+	SqlDatasourceMaxIdleConnsDefault    int
+	SqlDatasourceMaxConnLifetimeDefault int
+
 	// Snapshots
 	SnapshotEnabled       bool
 	ExternalSnapshotUrl   string
@@ -1115,6 +1120,7 @@ func (cfg *Cfg) Load(args CommandLineArgs) error {
 	}
 
 	cfg.readDataSourcesSettings()
+	cfg.readSqlDataSourceSettings()
 
 	cfg.DashboardPreviews = readDashboardPreviewsSettings(iniFile)
 	cfg.Storage = readStorageSettings(iniFile)
@@ -1837,6 +1843,13 @@ func (cfg *Cfg) readDataSourcesSettings() {
 	cfg.DataSourceLimit = datasources.Key("datasource_limit").MustInt(5000)
 }
 
+func (cfg *Cfg) readSqlDataSourceSettings() {
+	sqlDatasources := cfg.Raw.Section("sql_datasources")
+	cfg.SqlDatasourceMaxOpenConnsDefault = sqlDatasources.Key("max_open_conns_default").MustInt(100)
+	cfg.SqlDatasourceMaxIdleConnsDefault = sqlDatasources.Key("max_idle_conns_default").MustInt(100)
+	cfg.SqlDatasourceMaxConnLifetimeDefault = sqlDatasources.Key("max_conn_lifetime_default").MustInt(14400)
+}
+
 func GetAllowedOriginGlobs(originPatterns []string) ([]glob.Glob, error) {
 	allowedOrigins := originPatterns
 	originGlobs := make([]glob.Glob, 0, len(allowedOrigins))