Update: Key Injection Readme (#29)

* add explanation docs

* add readme for keyinject

* rm  from header

roles/key_inject/README.md

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 # key_inject ansible role
 
+This Ansible role is designed to facilitate the injection of cryptographic keys
+into Polkadot nodes, a crucial step for setting up a node for active
+participation in network operations like consensus and block authoring. This is
+meant only for development and testing purposes and use is not recommended in 
+production.
+
+## Key Role Functionality
+The `key_inject` role consists of several tasks organized into specific YAML
+files to streamline the process of key management on a Polkadot node:
+
+### Key Tasks and Files
+- **check_session_key.yml**: Checks whether session keys are present in the
+  node’s keystore.
+- **inject.yml**: Manages the injection of keys that are not found in the
+  keystore.
+- **main.yml**: Coordinates the flow between checking and injecting keys.
+
+### Detailed Process
+1. **Key Generation**:
+   - Generates session keys from specified private keys using
+   `paritytech.chain.subkey_inspect`, defaulting to the `sr25519` cryptographic
+   scheme.
+
+2. **Key Verification**:
+   - An RPC call checks for the presence of keys in the keystore. If absent,
+   the process retries up to 12 times, with a 10-second pause between each try.
+
+3. **Key Injection**:
+   - If keys are missing in the keystore, they are injected via an RPC call.
+   This includes handling for errors and notifications for service restarts
+   after successful injections.
+
+4. **Results Reporting**:
+   - Outcomes of the injection process are logged, indicating the success or
+   failure of the key injections.
+
+### Security and Risk Considerations
+Using Ansible for key management is feasible but must be approached with caution,
+particularly on networks with real economic value:
+- **Secure Storage**: Keys should be encrypted and securely stored within
+  Ansible variables. Use `ansible-vault encrypt` for sensitive data.
+- **Unique Keys**: Ensure no key sharing across nodes to avoid risks like
+  slashing.
+
+**Risk of Slashing**: There's a high risk of slashing in production if keys are
+mismanaged, particularly from issues like double-signing due to key reuse.
+
+**Best Practice**: In production environments, the use of `author_rotateKeys`
+RPC method is strongly recommended over manual methods to mitigate risks.
+This method ensures keys are managed securely, preventing equivocation.
+If `author_rotateKeys` is not utilized, consider implementing robust key
+management server software that provides safeguards against key misuse and 
+equivocation.
+
+## Usage Instructions
+```bash
+# playbooks/inject_keys.yaml
+---
+- name: Inject keys into Polkadot nodes
+  hosts: polkadot
+  gather_facts: false
+  tasks:
+    - name: Inject keys
+      ansible.builtin.include_role:
+        name: paritytech.chain.key_inject
+```
+```bash
+# group_vars/polkadot.yaml
+subkey_path: "https://releases.parity.io/substrate/x86_64-debian:stretch/v3.0.0/subkey/subkey"
+key_inject_relay_chain_rpc_port: 9944
+key_inject_relay_chain_key_list:
+  - scheme: "sr25519"
+    type: "gran"
+    priv_key: "0xcc...9123//1//grandpa"
+  - type: "babe"
+    priv_key: "SECRET SEED"
+  - type: "imon"
+    priv_key: "SECRET SEED"
+  - type: "para"
+    priv_key: "SECRET SEED"
+  - type: "asgn"
+    priv_key: "SECRET SEED"
+  - type: "audi"
+    priv_key: "SECRET SEED"
+key_inject_check_session_key: true
+```
+
+## Additional Resources
+This role supports a structured approach to key management but should only be
+used with a clear understanding of the security requirements and potential
+consequences like [slashing for equivocation](https://wiki.polkadot.network/docs/maintain-guides-avoid-slashing#equivocation).
+For further details on cryptographic practices in Polkadot, visit
+[Cryptography on Polkadot](https://wiki.polkadot.network/docs/learn-cryptography).