feat(sessions): permission co-signer API

docs/specs/servers/blockchain/blockchain-permissions-api.md

@@ -174,3 +174,84 @@ The POST request body should be in JSON format and following schema:
 
 * `400 Bad request` - Wrong format in request.
 * `401 Unauthorized` - Wrong signature.
+
+## Co-signing
+
+Co-signing request
+
+`POST /v1/sessions/{address}/sign?projectId={projectId}`
+
+* `address` - CAIP-10 address format.
+* `projectId` - Required. The project identifier.
+
+### Request body:
+
+The POST request body should be in JSON format and following schema:
+
+```typescript
+{
+	pci: string, // Permission controller identifier.
+	userOp: // ERC-4337 pseudo transaction object for v0.7:
+  {
+    sender: string, // The address of the smart contract account.
+    nonce: number, // Anti-replay protection; also used as the salt for first-time account creation.
+    callData: string, // Data that's passed to the sender for execution.
+    callGasLimit: number, // Gas limit for execution phase.
+    verificationGasLimit: number, // Gas limit for verification phase.
+    preVerificationGas: number, // Gas to compensate the bundler.
+    maxPriorityFeePerGas: number, // Maximum priority fee per gas (similar to EIP-1559 max_priority_fee_per_gas).
+    maxFeePerGas: number, // Maximum fee per gas (similar to EIP-1559(opens in a new tab) max_fee_per_gas).
+    signature: string, // Signature of all `userOp` fields hashed by keccak256 and signed by the key provided during the permission creation.
+    factory?: string, // Factory address if deploying a new sender contract.
+    factoryData?: string, // Data call for the factory.
+    paymaster?: string, // Paymaster address
+    paymasterVerificationGasLimit?: number, // Paymaster gas limits for the verification
+    paymasterPostOpGasLimit?: number, // Paymaster operation gas limit
+    paymasterData?: string // Bytes calldata for paymaster
+  }
+}
+```
+
+#### Success response body:
+
+Response will contain user operation transaction hash.
+
+```typescript
+{
+    userOperationTxHash: string // User operation transaction hash
+}
+```
+
+#### Response error codes:
+
+* `400 Bad request` - Invalid format in request.
+* `401 Unauthorized` - Invalid signature.
+
+## Get the transaction receipt 
+
+Get the user operation transaction receipt based on the transaction hash from `Co-signing`
+request.
+
+`GET /v1/sessions/{address}/receipt?projectId={projectId}&userOpTxHash={hash}`
+
+* `projectId` - Required. The project identifier.
+* `userOpTxHash` - User operation transaction hash to look for the receipt.
+
+#### Success response body:
+
+Response will contain user operation transaction hash receipt object.
+
+```typescript
+{
+    receipt: object
+}
+```
+
+If the transaction is not done yet, the server will respond with the `HTTP 202` code:
+
+* `202 Accepted` - Transaction receipt is not yet available (tx is processing), please try again later.
+
+#### Response error codes:
+
+* `400 Bad request` - Wrong format in request.
+* `401 Unauthorized` - Wrong signature.