Create cdk-pp-highlevel-arch.md

Add CDK PP high level architecture doc

Author: EmpieichO

docs/cdk/architecture/cdk-pp-highlevel-arch.md

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+The figure below depicts a simplified, high level view of the CDK PP chain architecture, as well as the flow of transactions through the system.
+
+![Figure: CDK PP Architecture](../../img/cdk/cdk-pp-architecture-001.png)
+
+## Transaction flow
+
+Here is a step by step flow of transactions starting from when users submit transactions up to when the transactions are settled in L1. 
+
+1. A user connects to the chain via a CDK Erigon RPC node and submits a transaction.
+2. CDK Erigon RPC node sends the transaction data to the transaction-pool manager.
+3. The transaction-pool manager proxies all transaction data to the CDK Erigon sequencer.
+4. CDK Erigon sequencer executes transactions, puts the transactions in blocks, and the blocks fill up batches. 
+5. CDK Erigon sequencer syncs all transaction data with any CDK Erigon RPC node.
+6. AggSender gets batch data from the CDK Erigon sequencer, uses the data to generate certificates, and submits the certificates to the JSON-RPC API.
+7. The JSON-RPC API checks validity of the certificates against the transaction data in the CDK Erigon RPC node.
+8. After validating the certificates, the JSON-RPC API sends a request to generate a proof, together with the necessary data (including the certificates), to the SP1 prover. 
+9. Once the proof is received from the SP1 prover, the JSON-RPC API sends it to L1.  
+
+
+
+## Sequential diagram
+
+The flow of data is depicted in the squential diagram below. 
+
+1. User submits a tx to the CDK Erigon RPC node.
+2. The CDK Erigon RPC node sends tx data to the tx-pool man.
+3. The tx-pool man proxies tx data to the CDK Erigon sequencer.
+4. CDK Erigon sequencer executes transactions.
+5. CDK Erigon sequencer syncs tx data with another CDK Erigon RPC node.
+6. AggSender gets batch data from the CDK Erigon sequencer.
+7. AggSender submits certificates to the JSON-RPC API.
+8. JSON-RPC API checks validity of the certificates.
+9. JSON-RPC API requests a proof from SP1 prover.
+10. SP1 prover sends back a proof.
+11. JSON-RPC API sends proof to L1.
+
+
+
+```mermaid
+sequenceDiagram
+    participant User
+    participant ErigonRPC1 as RPC node 1
+    participant tx-pool-man as tx-pool manager
+    participant Sequencer as Sequencer node
+    participant ErigonRPC2 as RPC node 2
+    participant AggSender as AggSender
+    participant API as JSON-RPC API
+    participant SP1-prover as SP1 prover
+    participant L1 as L1
+
+    User->>ErigonRPC1: submits tx
+    ErigonRPC1->>tx-pool-man: sends tx data 
+    tx-pool-man->>Sequencer: proxies tx data
+    Sequencer->>Sequencer: sequences transactions
+    Sequencer->>ErigonRPC2: syncs data
+    AggSender->>Sequencer: reads batch data
+    AggSender->>API: sends certificates
+    API->>ErigonRPC2: checks validity
+    API->>SP1-prover: requests proof
+    SP1-prover->>API: returns proof 
+    API->>L1: submits proof
+```