Fix label treatment of related charms (#277)

* fetch-lib

* Add cos-tool to charm

* only insert labels that do not already exist

* fetch-lib

.gitignore

@@ -8,3 +8,4 @@ __pycache__/
 .idea/
 tests/integration/*-tester/lib/
 .env
+cos-tool*

INTEGRATING.md

@@ -75,13 +75,13 @@ requires:
 2. Obtain the library from charmhub:
 
 ```shell
-charmcraft fetch-lib charms.loki_k8s.v0.loki_push_api
+charmcraft fetch-lib charms.loki_k8s.v1.loki_push_api
 ```
 
 3. Import the library and use it in your `src/charm.py`:
 
 ```python
-from charms.loki_k8s.v0.loki_push_api import LogProxyConsumer
+from charms.loki_k8s.v1.loki_push_api import LogProxyConsumer
 ...
 
 class MyOperatorCharm(CharmBase):

charmcraft.yaml

@@ -32,3 +32,11 @@ parts:
     - pkg-config
     - rustc
     - cargo
+  cos-tool:
+    plugin: dump
+    source: .
+    build-packages:
+      - curl
+    override-pull: |
+      curl -L -O https://github.com/canonical/cos-tool/releases/latest/download/cos-tool-${CRAFT_TARGET_ARCH}
+      chmod +x cos-tool-*