Rearrange the code a bit

I'm prepping to make bebot do more things than just be a gitlab webhook
handler, so I've moved the gitlab stuff into its own module (and some of
the matrix helper functions too, for good measure).

The config file also now puts all the gitlab-specific configuration
under a 'gitlab' key.

sample-config.yaml

@@ -2,57 +2,59 @@
 bind_address: 127.0.0.1
 # Port the webhook listener should bind to (default is 3000).
 bind_port: 3000
-# Optional prefix to serve the webhook path under (default is empty string).
-url_prefix: "/bebot"
 # Matrix user to sign in as.
 user_id: "@mybebot:example.com"
 # Password for Matrix user.
 password: "secret-matrix-account-password"
-# Default Matrix room to publish events to.
-default_room: "#my-project-commits:example.com"
-# Default set of events to publish.  If left out, all events will be published.
-default_publish_events:
-  - name: push
-    # Regexes of branch names.  Leave out entirely for "all branches".
-    branches:
-      - '^main$'
-      - '^xfce-.+'
-  - name: tag_push
-  - name: issues
-    # See the Gitlab docs for a full list of actions.  If left out, all actions
-    # will be published.
-    actions:
-      - open
-      - close
-  - name: merge_request
-    # See the Gitlab docs for a full list of actions.  If left out, all actions
-    # will be published.
-    actions:
-      - open
-      - merge
-  - name: pipeline
-    # See the Gitlab docs for a full list of statuses.  If left out, all
-    # actions will be published.
-    statuses:
-      - failed
-# Key-value configuration for repositories.
-repo_configs:
-  # Keys are the instance name / namespace / repository name
-  "gitlab.example.com/myorg/my-cool-app":
-    # Each repository should use a unique, randomly-generated token.  Enter
-    # this token in the webhook configuration's "Secret token" on Gitlab.
-    token: "abcdefg12345"
-    # You can override the default_room above.  Leave out to use the default.
-    room: "#my-cool-app-events:example.com"
-    # You can override default_events above.  Leave out this section to
-    # use the defaults.
-    publish_events:
-      - name: push
-        branches:
-          - main
-      - name: pipeline
-        statuses:
-          - failed
-  "gitlab.example.com/myuser/some-other-less-cool-app":
-    token: "kljaslkdjaklsdjalksd"
-    # This repo uses the default events and room.
+# All Gitlab-specific settings are under here.
+gitlab:
+  # Optional prefix to serve the webhook path under (default is empty string).
+  url_prefix: "/bebot"
+  # Default Matrix room to publish Gitlab events to.
+  default_room: "#my-project-commits:example.com"
+  # Default set of events to publish.  If left out, all events will be published.
+  default_publish_events:
+    - name: push
+      # Regexes of branch names.  Leave out entirely for "all branches".
+      branches:
+        - '^main$'
+        - '^xfce-.+'
+    - name: tag_push
+    - name: issues
+      # See the Gitlab docs for a full list of actions.  If left out, all actions
+      # will be published.
+      actions:
+        - open
+        - close
+    - name: merge_request
+      # See the Gitlab docs for a full list of actions.  If left out, all actions
+      # will be published.
+      actions:
+        - open
+        - merge
+    - name: pipeline
+      # See the Gitlab docs for a full list of statuses.  If left out, all
+      # actions will be published.
+      statuses:
+        - failed
+  # Key-value configuration for repositories.
+  repo_configs:
+    # Keys are the instance name / namespace / repository name
+    "gitlab.example.com/myorg/my-cool-app":
+      # Each repository should use a unique, randomly-generated token.  Enter
+      # this token in the webhook configuration's "Secret token" on Gitlab.
+      token: "abcdefg12345"
+      # You can override the default_room above.  Leave out to use the default.
+      room: "#my-cool-app-events:example.com"
+      # You can override default_events above.  Leave out this section to
+      # use the defaults.
+      publish_events:
+        - name: push
+          branches:
+            - main
+        - name: pipeline
+          statuses:
+            - failed
+    "gitlab.example.com/myuser/some-other-less-cool-app":
+      token: "kljaslkdjaklsdjalksd"
+      # This repo uses the default events and room.