Refactoring and API (#505)

Add JSON API with two flavors: input (what we get from "forks") and output
  (available at at `/v0/naucse.json`)
* The API is described and validated using jsonschema.
* Uses HTML for content, never Markdown.
* Relative URLs use a custom `naucse:` schema for the API. This gets converted
  in the HTML "sanitization" step.
* The API is v0; consumers are expected to coordinate with us until it is
  finalized.


The part that should be in "forks" is moved to the `naucse_render` module,
which became its own repo & PyPI package.


When one course's build fails, everything fails. No silent "an error occured"
pages.
* Only fully applies in "freeze mode" (with `NAUCSE_FREEZE=1`, or Flask
  in non-debug mode).
* In debug mode, lessons are rendered on demand instead of at startup.


Doesn't do fancy guessing of repo URL&branch for edit info.
Use `NAUCSE_MAIN_REPO_URL` and `NAUCSE_MAIN_REPO_BRANCH` if needed
(e.g. on Travis).


The model is better defined. Notably:
* A *course* has a list of *sessions*
* A session has a list of *materials*
* A material may be for a *lesson* (or an external link)
* A course (!) has *lessons* (which are referenced by materials).
  (All lessons are in a course; there's a special hidden `lessons` course
  containing the "local"/"canonical" lessons.)


The distinction between forks and local content is disappearing (but still
present).


The distinction between "courses" and "runs" in the model is disappearing:
mostly they just have different slugs (e.g. `courses/mi-pyt` vs.
`2018/pyladies-brno-jaro`) and are in different collections for lookup.


Instead of `FORKS_ENABLED=true`, there's `NAUCSE_TRUSTED_REPOS='*'`.
You can filter allowed repos a bit (docs TODO).


The model is different (`converters.py` is utilities for stuff you can
load/dump from/to a versioned JSON API).


Pages request LaTeX using "`modules: {'katex': '0.7.1'}`.
This should become a general mechanism to request some extra functionality
(like JS/CSS).


Model objects have info about their URLs.

---

PR & review: #505
Helps resolve: #494

Thanks to Miro Hrnočok, Petr Messner and Mikuláš Poul for review and minor fixes.

Author: encukou

.travis.yml

@@ -12,9 +12,10 @@ before_script:  # encrypted variables aren't accessible in PRs
 - 'if [ -n "$DOCKER_HUB_PASSWORD" ]; then docker login -u "$DOCKER_HUB_USERNAME" -p "$DOCKER_HUB_PASSWORD"; fi'
 - 'if [ -z "$DOCKER_HUB_PASSWORD" ]; then export ARCA_BACKEND_REGISTRY_PULL_ONLY=true; fi'
 script:
+- export NAUCSE_MAIN_REPO_URL=https://github.com/$TRAVIS_REPO_SLUG
+- export NAUCSE_MAIN_REPO_BRANCH=$TRAVIS_BRANCH
 - pipenv graph
 - pipenv run test
-- pipenv run naucse list-courses  # don't remove, there might be timeouts otherwise, see naucse/cli.py for details
 # we utilize our own timeout here to fail the build and store the cache
 # Travis CI would kill the entire job in 50 minutes, so we exit this after 40, to leave 10 minutes for setup + cache upload
 - timeout 2400 pipenv run naucse freeze --verbose
@@ -34,7 +35,7 @@ env:
   global:
   - secure: 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
   - ARCA_BACKEND=arca.backend.DockerBackend
-  - FORKS_ENABLED=true
+  - NAUCSE_TRUSTED_REPOS=*
   - DOCKER_HUB_USERNAME=naucse
   - secure: 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
 services:

Pipfile

@@ -18,7 +18,7 @@ mistune = "*"
 nbconvert = "*"
 python-dateutil = "*"
 traitlets = "*"
-arca = {extras = ["docker"], version = ">= 0.3"}
+arca = {extras = ["docker"],version = ">= 0.3"}
 cssutils = "*"
 click = "*"
 giturlparse = "*"
@@ -30,8 +30,10 @@ jupyter_client = "*"
 Pygments = "*"
 Werkzeug = "*"
 GitPython = "*"
+jsonschema = "*"
 lxml = "*"
 pygments-pytest = "*"
+naucse-render = "<1.0"
 
 [dev-packages]
 pytest = "*"

Pipfile.lock

@@ -70,7 +70,7 @@ Jestli ne, modul `tkinter` ještě nainstaluj:
   ```
   {% endfilter %}
 * **Ubuntu**:
-  {% filter markdown(inline=True) %}
+  {% filter markdown %}
   ```console
   $ sudo apt-get install python3-tk
   ```