compose.yaml: autopair first-party leader

To enable the demo workflow, users will need to pair two aggregators
with the control plane. Further, one of them must be first-party, which
can only be done using a CLI built with feature `admin`. But the one we
distribute via GitHub releases isn't, and I argue it shouldn't be, which
means that demo users can't appropriately pair aggregators.

We could provide a `curl` or `wget` command that'd do it, but as it
turns out, we already bundle the `divviup` CLI in the `divviup_api`
container, so let's just use that, since the API URL and token for the
aggregators are static!

I'm thinking we should have the demo user pair the other aggregator
themselves with `divviup` to simulate what they might have to do in a
realistic use case, if they bring their own helper.

This commit:

- adds feature `admin` to builds of `divviup_api_integration_test` in
  `docker-release.yaml` so that the bundled CLI will have
  `--first-party` and `--shared`
- adds a service `pair_aggregator` to `compose.yaml` that uses the
  `/divviup` entrypoint to pair `janus_1_aggregator` as a first-party,
  shared aggregator
- adds a stanza for `pair_aggregator` to `compose.dev.override.yaml`
- makes `compose.dev.override.yaml` build all images with features
  `integration_test,admin`

Part of #1096

.github/workflows/docker-release.yml

@@ -10,7 +10,7 @@ jobs:
       matrix:
         image: [
           { name: "divviup_api", rust_features: "default" },
-          { name: "divviup_api_integration_test", rust_features: "integration-testing" },
+          { name: "divviup_api_integration_test", rust_features: "integration-testing,admin" },
         ]
     permissions:
       id-token: write

compose.dev.override.yaml

@@ -1,31 +1,40 @@
 # Overrides for the local development docker compose setup. Meant only to be used by
 # compose.dev.yaml
 
+x-build: &build
+  build:
+    context: .
+    args:
+      RUST_PROFILE: dev
+      # We don't need both of these features in all three services, but it allows reusing one
+      # container image for both this and the divviup_api service.
+      RUST_FEATURES: integration-testing,admin
+
 services:
   divviup_api:
     image: !reset null
-    build:
-      context: .
-      args:
-        RUST_PROFILE: dev
-        RUST_FEATURES: integration-testing
+    <<: *build
     develop:
       watch:
         - path: src/
           action: rebuild
 
   divviup_api_migrate:
     image: !reset null
-    build:
-      context: .
-      args:
-        RUST_PROFILE: dev
-        # This isn't strictly required for migrations, but it allows reusing one container image
-        # for both this and the divviup_api service.
-        RUST_FEATURES: integration-testing
+    <<: *build
     develop:
       watch:
         - path: migration
           action: rebuild
           ignore:
             - README.md
+
+  pair_aggregator:
+    image: !reset null
+    <<: *build
+    develop:
+      watch:
+        - path: cli/
+          action: rebuild
+        - path: client/
+          action: rebuild

compose.yaml

@@ -53,6 +53,28 @@ services:
       postgres:
         condition: service_started
 
+  pair_aggregator:
+    image: ${DIVVIUP_API_IMAGE:-us-west2-docker.pkg.dev/divviup-artifacts-public/divviup-api/divviup_api_integration_test:0.3.12}
+    entrypoint:
+      - /divviup
+      - --url=http://localhost:8080
+      - --token=""
+      - aggregator
+      - create
+      - --name=leader
+      - --api-url=http://janus_1_aggregator:8080/aggregator-api
+      - --bearer-token=0000
+      - --first-party
+      - --shared
+    network_mode: service:divviup_api
+    depends_on:
+      divviup_api:
+        condition: service_healthy
+      janus_1_aggregator:
+        condition: service_healthy
+      janus_2_aggregator:
+        condition: service_healthy
+
   divviup_api:
     image: ${DIVVIUP_API_IMAGE:-us-west2-docker.pkg.dev/divviup-artifacts-public/divviup-api/divviup_api_integration_test:0.3.12}
     ports: