feat: Add CoinMarketCap external API (#2971)

## What ❔

Adds support for CoinMarketCap as a price API for base token prices.

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## Why ❔

Currently, the only supported API is CoinGecko. It's not ideal to only
support a single 3rd party API here, so this provides some more degrees
of freedom, and makes base token less reliant on a single third-party
provider.

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are the principles behind them? -->
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## Checklist

<!-- Check your PR fulfills the following items. -->
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- [x] PR title corresponds to the body of PR (we generate changelog
entries from PRs).
- [x] Tests for the changes have been added / updated. (See #2970)
- [x] Documentation comments have been added / updated.
- [x] Code has been formatted via `zk fmt` and `zk lint`.

core/bin/zksync_server/src/node_builder.rs

@@ -19,9 +19,7 @@ use zksync_node_framework::{
     implementations::layers::{
         base_token::{
             base_token_ratio_persister::BaseTokenRatioPersisterLayer,
-            base_token_ratio_provider::BaseTokenRatioProviderLayer,
-            coingecko_client::CoingeckoClientLayer, forced_price_client::ForcedPriceClientLayer,
-            no_op_external_price_api_client::NoOpExternalPriceApiClientLayer,
+            base_token_ratio_provider::BaseTokenRatioProviderLayer, ExternalPriceApiLayer,
         },
         circuit_breaker_checker::CircuitBreakerCheckerLayer,
         commitment_generator::CommitmentGeneratorLayer,
@@ -557,24 +555,8 @@ impl MainNodeBuilder {
 
     fn add_external_api_client_layer(mut self) -> anyhow::Result<Self> {
         let config = try_load_config!(self.configs.external_price_api_client_config);
-        match config.source.as_str() {
-            CoingeckoClientLayer::CLIENT_NAME => {
-                self.node.add_layer(CoingeckoClientLayer::new(config));
-            }
-            NoOpExternalPriceApiClientLayer::CLIENT_NAME => {
-                self.node.add_layer(NoOpExternalPriceApiClientLayer);
-            }
-            ForcedPriceClientLayer::CLIENT_NAME => {
-                self.node.add_layer(ForcedPriceClientLayer::new(config));
-            }
-            _ => {
-                anyhow::bail!(
-                    "Unknown external price API client source: {}",
-                    config.source
-                );
-            }
-        }
-
+        self.node
+            .add_layer(ExternalPriceApiLayer::try_from(config)?);
         Ok(self)
     }
 

core/lib/external_price_api/Cargo.toml

@@ -20,8 +20,12 @@ serde.workspace = true
 reqwest = { workspace = true, features = ["json"] }
 fraction.workspace = true
 rand.workspace = true
+tracing.workspace = true
 
 zksync_config.workspace = true
 zksync_types.workspace = true
 tokio.workspace = true
+
+[dev-dependencies]
 httpmock.workspace = true
+serde_json.workspace = true