Docs code links (#7342)

* Update docs

- Add note about permission denied error

* Add macro for generating link to github code

* Implement similar feature for source directory links

* Adds helper function for link checking

* Allow for specification of "raw" file links

* Remove debug statement

* Generate list of available invoke tasks

docs/docs/extend/plugins.md

@@ -16,7 +16,7 @@ For further information, read more about [installing plugins](./plugins/install.
 
 ### Plugin Base Class
 
-Custom plugins must inherit from the [InvenTreePlugin class](https://github.com/inventree/InvenTree/blob/2d1776a151721d65d0ae007049d358085b2fcfd5/InvenTree/plugin/plugin.py#L204). Any plugins installed via the methods outlined above will be "discovered" when the InvenTree server launches.
+Custom plugins must inherit from the [InvenTreePlugin class]({{ sourcefile("src/backend/InvenTree/plugin/plugin.py") }}). Any plugins installed via the methods outlined above will be "discovered" when the InvenTree server launches.
 
 !!! warning "Namechange"
     The name of the base class was changed with `0.7.0` from `IntegrationPluginBase` to `InvenTreePlugin`. While the old name is still available till `0.8.0` we strongly suggest upgrading your plugins. Deprecation warnings are raised if the old name is used.
@@ -28,7 +28,7 @@ Please read all release notes and watch out for warnings - we generally provide
 
 #### Plugins
 
-General classes and mechanisms are provided under the `plugin` [namespaces](https://github.com/inventree/InvenTree/blob/master/src/backend/InvenTree/plugin/__init__.py). These include:
+General classes and mechanisms are provided under the `plugin` [namespaces]({{ sourcefile("src/backend/InvenTree/plugin/__init__.py") }}). These include:
 
 ```python
 # Management objects
@@ -44,7 +44,7 @@ MixinNotImplementedError    # Is raised if a mixin was not implemented (core mec
 
 #### Mixins
 
-Mixins are split up internally to keep the source tree clean and enable better testing separation. All public APIs that should be used are exposed under `plugin.mixins`. These include all built-in mixins and notification methods. An up-to-date reference can be found in the source code (current master can be [found here](https://github.com/inventree/InvenTree/blob/master/src/backend/InvenTree/plugin/mixins/__init__.py)).
+Mixins are split up internally to keep the source tree clean and enable better testing separation. All public APIs that should be used are exposed under `plugin.mixins`. These include all built-in mixins and notification methods. An up-to-date reference can be found in the source code [can be found here]({{ sourcefile("src/backend/InvenTree/plugin/mixins/__init__.py") }}).
 
 #### Models and other internal InvenTree APIs
 
@@ -72,7 +72,7 @@ MIN_VERSION = None  # Lowest InvenTree version number that is supported by the p
 MAX_VERSION = None  # Highest InvenTree version number that is supported by the plugin
 ```
 
-Refer to the [sample plugins](https://github.com/inventree/InvenTree/tree/master/src/backend/InvenTree/plugin/samples) for further examples.
+Refer to the [sample plugins]({{ sourcedir("src/backend/InvenTree/plugin/samples") }}) for further examples.
 
 ### Plugin Config
 

docs/docs/extend/plugins/locate.md

@@ -28,7 +28,7 @@ If a locate plugin is installed and activated, the [InvenTree mobile app](../../
 
 ### Implementation
 
-Refer to the [InvenTree source code](https://github.com/inventree/InvenTree/blob/master/src/backend/InvenTree/plugin/samples/locate/locate_sample.py) for a simple implementation example.
+Refer to the [InvenTree source code]({{ sourcefile("src/backend/InvenTree/plugin/samples/locate/locate_sample.py") }}) for a simple implementation example.
 
 ### Sample Plugin
 

docs/docs/extend/plugins/urls.md

@@ -65,7 +65,7 @@ Additionally, add the following imports after the extended line.
 #### Blocks
 The page_base file is split into multiple sections called blocks. This allows you to implement sections of the webpage while getting many items like navbars, sidebars, and general layout provided for you.
 
-The current default page base can be found [here](https://github.com/inventree/InvenTree/blob/master/src/backend/InvenTree/templates/page_base.html). Look through this file to determine overridable blocks. The [stock app](https://github.com/inventree/InvenTree/tree/master/src/backend/InvenTree/stock) offers a great example of implementing these blocks.
+The current default page base can be found [here]({{ sourcefile("src/backend/InvenTree/templates/page_base.html") }}). Look through this file to determine overridable blocks. The [stock app]({{ sourcedir("src/backend/InvenTree/stock") }}) offers a great example of implementing these blocks.
 
 !!! warning "Sidebar Block"
     You may notice that implementing the `sidebar` block doesn't initially work. Be sure to enable the sidebar using JavaScript. This can be achieved by appending the following code, replacing `label` with a label of your choosing,  to the end of your template file.

docs/docs/extend/plugins/validation.md

@@ -9,7 +9,7 @@ The `ValidationMixin` class enables plugins to perform custom validation of obje
 Any of the methods described below can be implemented in a custom plugin to provide functionality as required.
 
 !!! info "More Info"
-    For more information on any of the methods described below, refer to the InvenTree source code. [A working example is available as a starting point](https://github.com/inventree/InvenTree/blob/master/src/backend/InvenTree/plugin/samples/integration/validation_sample.py).
+    For more information on any of the methods described below, refer to the InvenTree source code. [A working example is available as a starting point]({{ sourcefile("src/backend/InvenTree/plugin/samples/integration/validation_sample.py") }}).
 
 !!! info "Multi Plugin Support"
     It is possible to have multiple plugins loaded simultaneously which support validation methods. For example when validating a field, if one plugin returns a null value (`None`) then the *next* plugin (if available) will be queried.