In order for a blueprint to work, it has to be registered with a Crow app before the app is run. This can be done using `#!cpp app.register_blueprint(blueprint);`.<br><br>
Blueprints let you do the following:<br><br>
### Define Routes
You can define routes in a blueprint, similarly to how `#!cpp CROW_ROUTE(app, "/xyz")` works, you can use `#!cpp CROW_BP_ROUTE(blueprint, "/xyz")` to define a blueprint route.
Blueprints can have a prefix assigned to them. This can be done when creating a new blueprint as in `#!cpp crow::blueprint bp("prefix");`. This prefix will be applied to all routes belonging to the blueprint, turning a route such as `/crow/rocks` into `/prefix/crow/rocks`.
Unlike routes, blueprint prefixes should contain no slashes.
### Use a custom Static directory
Blueprints let you define a custom static directory (relative to your working directory). This can be done by initializing a blueprint as `#!cpp crow::blueprint bp("prefix", "custom_static");`. This does not have an effect on `#!cpp set_static_file_info()`, it's only for when you want direct access to a file.
Currently changing which endpoint the blueprint uses isn't possible, so whatever you've set in `CROW_STATIC_ENDPOINT` (default is "static") will be used. Making your final route `/prefix/static/filename`.
### Use a custom Templates directory
Similar to static directories, You can set a custom templates directory (relative to your working directory). To do this you initialize the blueprint as `#!cpp crow::blueprint bp("prefix", "custom_static", "custom_templates");`. Any routes defined for the blueprint will use that directory when calling `#!cpp crow::mustache::load("filename.html")`.
If you want to define a custom templates directory without defining a custom static directory, you can pass the static directory as an empty string. Making your constructor `#!cpp crow::blueprint bp("prefix", "", "custom_templates");`.
You can define a custom catchall route for a blueprint by calling `#!cpp CROW_BP_CATCHALL_ROUTE(blueprint)`. This causes any requests with a URL starting with `/prefix` and no route found to call the blueprint's catchall route. If no catchall route is defined, Crow will default to either the parent blueprint or the app's catchall route.
Blueprints can also register other blueprints. This is done through `#!cpp blueprint.register_blueprint(blueprint_2);`. The child blueprint's routes become `/prefix/prefix_2/abc/xyz`.
