feat(network-subgraphs): Add idAsString field (#994)

Added new field to `Stream` entity: `Stream#idAsString`. It has same
value as in the `id` field. The field allows us do to substring queries
for the field id (by using `idAsString_contains` where clause).

This feature is needed e.g. in
streamr-dev/network#3132.

Author: teogeb

packages/network-subgraphs/schema.graphql

@@ -35,6 +35,8 @@ type StreamPermission @entity {
 type Stream @entity {
   "stream ID = 'creator address'/'path' where path can be any string"
   id: ID!
+  "This field has the same value as the ID field. It enables us to perform substring queries on the id field using the idAsString_contains where clause"
+  idAsString: String! @index
   "Stream metadata JSON"
   metadata: String!
   "Permissions that each Ethereum address owns to this stream"

packages/network-subgraphs/src/streamRegistry.ts

@@ -24,6 +24,7 @@ export function handleStreamCreation(event: StreamCreated): void {
         return
     }
     let stream = new Stream(event.params.id)
+    stream.idAsString = event.params.id,
     stream.metadata = event.params.metadata
     stream.createdAt = event.block.timestamp
     stream.updatedAt = event.block.timestamp