Merge pull request #3555 from dfinity/add-secret-key

add: info about using keys with Node.js

docs/developer-docs/developer-tools/off-chain/agents/javascript-agent.mdx

@@ -462,4 +462,4 @@ export const backend_canister = createActor(canisterId);
 
 - [`agent-js` documentation](https://agent-js.icp.xyz/agent/modules.html).
 
-- [`agent-js` npm package](https://www.npmjs.com/package/@dfinity/agent).
+- [`agent-js` npm package](https://www.npmjs.com/package/@dfinity/agent).

docs/developer-docs/developer-tools/off-chain/agents/nodejs.mdx

@@ -16,7 +16,16 @@ import { MarkdownChipRow } from "/src/components/Chip/MarkdownChipRow";
 
 ## Identity management
 
-Before you set up an actor, you will need to have an identity. You can set up an identity that will resolve a seed phrase to a principal by using the following code:
+Before you set up an actor, you will need to have an identity.
+
+### Using keys through `agent-js`
+
+You can configure an authentication identity for Node.js through `agent-js`'s using the ECDSA or Ed25519 private keys. [Learn more in the agent-js docs](https://internetcomputer.org/docs/current/developer-docs/developer-tools/off-chain/agents/javascript-agent).
+
+
+### Seed phrase
+
+Alternatively, you can set up an identity that will resolve a seed phrase to a principal by using the following code:
 
 ```js
 // identity.js
@@ -35,7 +44,6 @@ The seed phrase in this example is derived from the word `test` repeated 12 time
 Remember to store any seed phrase you use in production in a secure place. Use environment variables, and never commit a real seed phrase in plain text to your codebase.
 :::
 
-
 ## Asset uploading
 
 A community library, `@dfinity/assets`, is available to upload assets to your project's asset canister. You'll need to get the canister ID, pass your agent, and then upload your files. Below is an example code snippet showcasing this workflow:
@@ -359,4 +367,4 @@ main();
 
 - [ic-websocket-js](https://www.npmjs.com/package/ic-websocket-js)
 
-- [End to end testing](https://internetcomputer.org/docs/current/tutorials/developer-journey/level-2/2.5-unit-testing#end-to-end-e2e-testing)
+- [End to end testing](https://internetcomputer.org/docs/current/tutorials/developer-journey/level-2/2.5-unit-testing#end-to-end-e2e-testing)