Added admin interface to manage channels and enabled plugins (#9)

* Added base admin login/logout flows

* Ignore local database

* Channel model

* Admin interface for channels and plugins

* Added database tests along with workflows

* Added some docstrings

* Ignore .coverage file

* Creating plugins docs WIP

* Documentation

* Black everything

* Some documentation

* Coverage for the plugins package as well

* DB Fixes

* Absolute FROM in Dockerfile

* Database and logging fixes

* Slack: Support private channels

* Added pre-commit

* black'd

* Fixed UserQuery.create

* Fixed ChannelPluginQuery.create exists call

* Added ChannelPlugin menu for debugging

* Ignore sqlite databases

* Updated contributing docs

.pre-commit-config.yaml

@@ -0,0 +1,22 @@
+repos:
+- repo: https://github.com/pre-commit/pre-commit-hooks
+  rev: v2.2.3
+  hooks:
+  - id: trailing-whitespace
+  - id: end-of-file-fixer
+  - id: flake8
+
+- repo: https://github.com/asottile/seed-isort-config
+  rev: v1.9.2
+  hooks:
+  - id: seed-isort-config
+- repo: https://github.com/pre-commit/mirrors-isort
+  rev: v4.3.20
+  hooks:
+  - id: isort
+
+- repo: https://github.com/ambv/black
+  rev: stable
+  hooks:
+  - id: black
+    language_version: python3