docs: multi-tenant development environment (#19650)

Co-authored-by: Trevor Whitney <trevorjwhitney@gmail.com>

README.md

@@ -123,6 +123,15 @@ $ make loki
 $ ./cmd/loki/loki -config.file=./cmd/loki/loki-local-config.yaml
 ```
 
+To run multiple Loki tenants locally, ensure that auth_enabled is set to true and provide a runtime config with any tenant specific overrides.
+```bash
+# Build binary
+$ make loki
+
+# Run executable
+./loki -config.file=./cmd/loki/loki-local-multi-tenant-config.yaml -runtime-config.file=./cmd/loki/loki-overrides.yaml
+```
+
 To build Promtail on non-Linux platforms, use the following command:
 
 ```bash

cmd/loki/loki-local-multi-tenant-config.yaml

@@ -0,0 +1,68 @@
+# auth_enabled is actually turning on multi-tenancy, otherwise all requests get routed to "fake" tenant
+auth_enabled: true
+
+server:
+  http_listen_port: 3100
+  grpc_listen_port: 9096
+  log_level: debug
+  grpc_server_max_concurrent_streams: 1000
+
+common:
+  instance_addr: 127.0.0.1
+  path_prefix: /tmp/loki
+  storage:
+    filesystem:
+      chunks_directory: /tmp/loki/chunks
+      rules_directory: /tmp/loki/rules
+  replication_factor: 1
+  ring:
+    kvstore:
+      store: inmemory
+
+query_range:
+  results_cache:
+    cache:
+      embedded_cache:
+        enabled: true
+        max_size_mb: 100
+
+limits_config:
+  metric_aggregation_enabled: true
+  max_global_streams_per_user: 0
+  ingestion_rate_mb: 50000
+  ingestion_burst_size_mb: 50000
+  volume_enabled: true
+
+schema_config:
+  configs:
+    - from: 2020-10-24
+      store: tsdb
+      object_store: filesystem
+      schema: v13
+      index:
+        prefix: index_
+        period: 24h
+
+pattern_ingester:
+  enabled: true
+  metric_aggregation:
+    loki_address: localhost:3100
+
+ruler:
+  alertmanager_url: http://localhost:9093
+
+frontend:
+  encoding: protobuf
+
+# By default, Loki will send anonymous, but uniquely-identifiable usage and configuration
+# analytics to Grafana Labs. These statistics are sent to https://stats.grafana.org/
+#
+# Statistics help us better understand how Loki is used, and they show us performance
+# levels for most users. This helps us prioritize features and documentation.
+# For more information on what's sent, look at
+# https://github.com/grafana/loki/blob/main/pkg/analytics/stats.go
+# Refer to the buildReport method to see what goes into a report.
+#
+# If you would like to disable reporting, uncomment the following lines:
+#analytics:
+#  reporting_enabled: false

cmd/loki/loki-overrides.yaml

@@ -0,0 +1,10 @@
+configs:
+  '1':
+    log_push_request: false
+    log_push_request_streams: false
+overrides:
+  '1':
+    allow_structured_metadata: true
+    pattern_persistence_enabled: true
+    volume_enabled: true
+    max_query_bytes_read: 1073741824