Adjust config structure according to feedback from code review

Signed-off-by: Christian Haudum <[email protected]>

docs/sources/shared/configuration.md

@@ -3391,7 +3391,8 @@ The `limits_config` block configures global and per-tenant limits in Loki. The v
 # Experimental: Detect fields from stream labels, structured metadata, or
 # json/logfmt formatted log line and put them into structured metadata of the
 # log entry.
-[discover_generic_fields: <map of string to list of strings>]
+discover_generic_fields:
+  [fields: <map of string to list of strings>]
 
 # If no service_name label exists, Loki maps a single label from the configured
 # list to service_name. If none of the configured labels exist in the stream,

pkg/validation/limits.go

@@ -86,7 +86,7 @@ type Limits struct {
 	IncrementDuplicateTimestamp bool             `yaml:"increment_duplicate_timestamp" json:"increment_duplicate_timestamp"`
 
 	// Metadata field extraction
-	DiscoverGenericFields map[string][]string `yaml:"discover_generic_fields" json:"discover_generic_fields" doc:"description=Experimental: Detect fields from stream labels, structured metadata, or json/logfmt formatted log line and put them into structured metadata of the log entry."`
+	DiscoverGenericFields FieldDetectorConfig `yaml:"discover_generic_fields" json:"discover_generic_fields" doc:"description=Experimental: Detect fields from stream labels, structured metadata, or json/logfmt formatted log line and put them into structured metadata of the log entry."`
 	DiscoverServiceName   []string            `yaml:"discover_service_name" json:"discover_service_name"`
 	DiscoverLogLevels     bool                `yaml:"discover_log_levels" json:"discover_log_levels"`
 	LogLevelFields        []string            `yaml:"log_level_fields" json:"log_level_fields"`
@@ -247,6 +247,10 @@ type Limits struct {
 	S3SSEKMSEncryptionContext string `yaml:"s3_sse_kms_encryption_context" json:"s3_sse_kms_encryption_context" doc:"nocli|description=S3 server-side encryption KMS encryption context. If unset and the key ID override is set, the encryption context will not be provided to S3. Ignored if the SSE type override is not set."`
 }
 
+type FieldDetectorConfig struct {
+	Fields map[string][]string `yaml:"fields" json:"fields"`
+}
+
 type StreamRetention struct {
 	Period   model.Duration    `yaml:"period" json:"period" doc:"description:Retention period applied to the log lines matching the selector."`
 	Priority int               `yaml:"priority" json:"priority" doc:"description:The larger the value, the higher the priority."`
@@ -999,7 +1003,7 @@ func (o *Overrides) IncrementDuplicateTimestamps(userID string) bool {
 }
 
 func (o *Overrides) DiscoverGenericFields(userID string) map[string][]string {
-	return o.getOverridesForUser(userID).DiscoverGenericFields
+	return o.getOverridesForUser(userID).DiscoverGenericFields.Fields
 }
 
 func (o *Overrides) DiscoverServiceName(userID string) []string {