add README to azure ip masq merger

Author: QxBytes

azure-ip-masq-merger/README.md

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+# azure-ip-masq-merger
+
+`azure-ip-masq-merger` is a utility for merging multiple ip-masq-agent configuration files into a single, valid configuration for use in Kubernetes clusters.
+
+## Description
+
+The goal of this program is to periodically scan a directory for configuration fragments (YAML or JSON files starting with `ip-masq`), validate and merge them, and write the resulting configuration to a target directory for consumption. This allows us to combine non-masquerade CIDRs and related options between multiple files, for example if we had one ip masq config managed by the cloud provider and another supplied by the user.
+
+## Usage
+
+Follow the steps below to build and run the program:
+
+1. Build the binary using `make`:
+    ```bash
+    make azure-ip-masq-merger
+    ```
+    or make an image:
+    ```bash
+    make azure-ip-masq-merger-image
+    ```
+
+2. Deploy or copy the binary to your node(s).
+
+3. Prepare your configuration fragments in the input directory (see below for defaults). Each file should be named with the prefix `ip-masq` and contain valid YAML or JSON for the ip-masq-agent config.
+
+4. Start the program with:
+    ```bash
+    ./azure-ip-masq-merger --input=/etc/config/ --output=/etc/merged-config/
+    ```
+    - The `--input` flag specifies the directory to scan for config fragments. Default: `/etc/config/`
+    - The `--output` flag specifies where to write the merged config. Default: `/etc/merged-config/`
+
+5. The merged configuration will be written to the output directory as `ip-masq-agent`. If no valid configs are found, any existing merged config will be removed.
+
+## Manual Testing
+
+You can test the merger locally by creating sample config files in your input directory and running the merger.
+
+## Configuration File Format
+
+Each config fragment should be a YAML or JSON file that may have the following fields:
+```yaml
+nonMasqueradeCIDRs:
+  - 10.0.0.0/8
+  - 192.168.0.0/16
+masqLinkLocal: true
+masqLinkLocalIPv6: false
+```
+- `nonMasqueradeCIDRs`: List of CIDRs that should not be masqueraded. Appended between configs.
+- `masqLinkLocal`: Boolean to enable/disable masquerading of link-local addresses. OR'd between configs.
+- `masqLinkLocalIPv6`: Boolean to enable/disable masquerading of IPv6 link-local addresses. OR'd between configs.
+
+## Debugging
+
+Logs are output to standard error. Increase verbosity with the `-v` flag:
+```bash
+./azure-ip-masq-merger -v 2
+```
+
+## Development
+
+To run tests:
+```bash
+go test ./...
+```
+or at the repository level:
+```bash
+make test-azure-ip-masq-merger
+```