grafana configmap generator tool added

hack/grafana-dashboards-configmap-generator/README.md

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+# Grafana Dashboards Configmap Generator
+
+## Description:
+Tool to maintain grafana dashboards' configmap for a grafana deployed with kube-prometheus (a tool inside prometheus-operator).
+
+The tool reads the content of a directory with grafana .json resources (dashboards and datasources) and creates a manifest file under output/ directory with all the content from the files in a Kubernetes ConfigMap format.
+
+Based on a configurable size limit, the tool will create 1 or N configmaps to allocate the .json resources (bin packing). If the limit is reached then the configmaps generated will have names like grafana-dashboards-0, grafana-dashboards-1, etc, and if the limit is not reached the configmap generated will be called "grafana-dashboards".
+
+Input Parameters Allowed:
+```bash
+-i dir, --input-dir dir
+  Directory with grafana dashboards to process.
+  Important notes:
+    Files should be suffixed with -dashboard.json or -datasource.json.
+    We don't recommend file names with spaces.
+
+-o file, --output-file file
+  Output file for config maps.
+
+-s NUM, --size-limit NUM
+  Size limit in bytes for each dashboard (default: 240000)
+
+-n namespace, --namespace namespace
+  Namespace for the configmap (default: monitoring).
+
+-x, --apply-configmap
+  Applies the generated configmap with kubectl.
+
+--apply-type
+  Type of kubectl command. Accepted values: apply, replace, create (default: apply).
+```
+
+## Usage
+
+Just execute the .sh under bin/ directory. The output will be placed in the output/ directory.
+
+Examples:
+```bash
+$ ./grafana_dashboards_generate.sh
+$ bin/grafana_dashboards_generate.sh -o manifests/grafana/grafana-dashboards.yaml -i assets/grafana-dashboards
+$ bin/grafana_dashboards_generate.sh -s 1000000 --apply-configmap --apply-type replace
+
+# Note: the output file, if provided with -o, shouldn't exist.
+```
+
+## Configuration and options
+
+* Put the json files you want to pack in the templates/grafana-dashboards/ directory
+* Size limit default is 240000 bytes due to the annotations size limit in kubernetes of 256KB.
+