feat: add code to retrieve sxt access token (#27)

chainlink-functions/README.md

@@ -8,5 +8,6 @@ This example is heavily borrowed from https://docs.chain.link/chainlink-function
     LINK_TOKEN_ADDRESS=0x779877A7B0D9E8603169DdbD7836e478b4624789 # REPLACE this with your wallet address
     ETHEREUM_SEPOLIA_RPC_URL=
     PRIVATE_KEY=
+    SXT_API_KEY=
     ```
 4. Run `node example/request.js` to upload the secrets, run a simulation, and then submit a chainlink job.

chainlink-functions/example/request.js

@@ -34,7 +34,7 @@ const makeRequestSepolia = async () => {
     .toString();
 
   const args = [];
-  const secrets = { apiKey: "TODO" }; // NOTE: be sure to modify source.js to use this secret properly when actually adding a secret.
+  const secrets = { apiKey: process.env.SXT_API_KEY };
   const slotIdNumber = 0; // slot ID where to upload the secrets
   const expirationTimeMinutes = 15; // expiration time in minutes of the secrets
   const gasLimit = 300000;

chainlink-functions/example/source.js

@@ -1,6 +1,24 @@
+
+// Ensure the API key is available
 if (!secrets.apiKey) {
   throw Error("API Key Not Found");
 }
 
-// NOTE: Do NOT use this apiKey here in production, it is only here to demonstrate secrets.
-return Functions.encodeString(secrets.apiKey);
+// Construct a payload to fetch an accesstoken to be used for
+// api access to the prover. It is a required component of the payload to 
+// receive a proof.
+// Set the secrets field to an apiKey that you own for your sxt account.
+
+// Execute the API request using Functions.makeHttpRequest
+const apiResponse = await Functions.makeHttpRequest({
+  url: "https://proxy.api.spaceandtime.dev/auth/apikey",
+  method: "POST",
+  headers: {
+    "apikey": secrets.apiKey,
+    "Content-Type": "application/json"
+  }
+});
+
+// Extract the access token, truncate it to 256 characters, and return it as an encoded string
+const accessToken = apiResponse.data.accessToken;
+return Functions.encodeString("TODO");