docs: Add more Stellar transaction submission examples (#424)

Signed-off-by: Dylan Kilkenny <dylankilkenny95@gmail.com>

Author: dylankilkenny

docs/modules/ROOT/pages/stellar.adoc

@@ -196,9 +196,10 @@ The relayer supports three ways to submit transactions:
 
 1. **Operations-based**: Build a transaction by specifying the `operations` array (recommended for most use cases)
 2. **Transaction XDR (unsigned)**: Submit a pre-built unsigned transaction using `transaction_xdr` field (advanced use case)
-3. **Transaction XDR (signed) with fee bump**: Submit a signed transaction using `transaction_xdr` with `fee_bump: true` to wrap it in a fee bump transaction
+3. **Transaction XDR (signed)**: Submit a signed transaction using `transaction_xdr` with `fee_bump: true` (required for signed XDR) to wrap it in a fee bump transaction
+
+==== Example 1: Operations-based Transaction
 
-Example: Send Transaction
 [source,bash]
 ----
 curl --location --request POST 'http://localhost:8080/api/v1/relayers/<stellar_relayer_id>/transactions' \
@@ -218,6 +219,56 @@ curl --location --request POST 'http://localhost:8080/api/v1/relayers/<stellar_r
 }'
 ----
 
+==== Example 2: Unsigned Transaction XDR
+
+Submit a pre-built unsigned transaction. The relayer will sign it with its configured signer:
+
+[source,bash]
+----
+curl --location --request POST 'http://localhost:8080/api/v1/relayers/<stellar_relayer_id>/transactions' \
+--header 'Authorization: Bearer <api_key>' \
+--header 'Content-Type: application/json' \
+--data-raw '{
+  "network": "testnet",
+  "transaction_xdr": "AAAAAgAAAACige4lTdwSB/sto4SniEdJ2kOa2X65s5bqkd40J4DjSwAAAGQAAHAkAAAADgAAAAAAAAAAAAAAAQAAAAAAAAABAAAAAKKB7iVN3BIH+y2jhKeIR0naQ5rZfrmzluqR3jQngONLAAAAAAAAAAAAD0JAAAAAAAAAAAA="
+}'
+----
+
+The `transaction_xdr` field should contain a base64-encoded unsigned transaction envelope. This is useful when:
+- You need precise control over transaction structure
+- You want to use advanced Stellar features not exposed via the operations API
+
+==== Example 3: Signed Transaction XDR
+
+Submit a pre-signed transaction with fee bump wrapper. **Note: `fee_bump: true` is required when submitting signed XDR**:
+
+[source,bash]
+----
+curl --location --request POST 'http://localhost:8080/api/v1/relayers/<stellar_relayer_id>/transactions' \
+--header 'Authorization: Bearer <api_key>' \
+--header 'Content-Type: application/json' \
+--data-raw '{
+  "network": "testnet",
+  "transaction_xdr": "AAAAAgAAAABjc+mbXCnvmVk4lxqVl7s0LAz5slXqmkHBg8PpH7p3DgAAAGQABpK0AAAACQAAAAAAAAAAAAAAAQAAAAAAAAABAAAAAGN0qQBW8x3mfbwGGYndt2uq4O4sZPUrDx5HlwuQke9zAAAAAAAAAAAAAA9CAAAAAQAAAAA=",
+  "fee_bump": true,
+  "max_fee": 10000000
+}'
+----
+
+The fee bump feature is useful when:
+- You have a pre-signed transaction from another system or wallet
+- You want the relayer to pay transaction fees on behalf of the original signer
+- You need to increase the fee for a transaction to ensure timely execution
+
+[IMPORTANT]
+====
+When using `transaction_xdr`:
+- The XDR must be properly formatted and valid for the target network
+- For unsigned XDR, the relayer will add its signature before submission
+- **For signed XDR, `fee_bump: true` is mandatory** - the relayer requires this to wrap the signed transaction in a fee bump envelope
+- The `max_fee` parameter (in stroops) controls the maximum fee for fee bump transactions (defaults to 1,000,000 = 0.1 XLM)
+====
+
 See link:https://release-v1-0-0%2D%2Dopenzeppelin-relayer.netlify.app/api_docs.html[API Reference^] for full details and examples.
 
 === Asset Types