exchange broker options

common/proto/exchange_rates.proto

@@ -2,6 +2,8 @@ syntax = "proto3";
 
 package komp_ac.exchange_rates;
 
+import "common.proto";
+
 // Selects WHICH DATE supplies the rate; this is independent of where the rate
 // comes from. These are not four user-facing choices: UNSPECIFIED is protobuf's
 // zero-value sentinel and is rejected when an explicit selection is supplied.
@@ -67,6 +69,10 @@ message ExchangeRateSelection {
 }
 
 service ExchangeRateService {
+  // Lists the direct-rate providers compiled into and registered by this
+  // server instance. Clients use these stable IDs when configuring profiles.
+  rpc ListRateSources(komp_ac.common.Empty)
+      returns (ListRateSourcesResponse);
   rpc PreviewDirectConversion(PreviewDirectConversionRequest)
       returns (PreviewDirectConversionResponse);
   rpc ListConversionEvidence(ListConversionEvidenceRequest)
@@ -77,6 +83,14 @@ service ExchangeRateService {
       returns (ProfileForeignCurrency);
 }
 
+message RateSourceProvider {
+  string id = 1;
+}
+
+message ListRateSourcesResponse {
+  repeated RateSourceProvider sources = 1;
+}
+
 message PreviewDirectConversionRequest {
   string original_amount = 1;
   string original_currency = 2;