add support for OGC API - Coverages (#110) (#516)

* add support for OGC API - Coverages

* fix coverage CRS ref

* fix ref to OACov schemas for testing

* move spectral testing to after_success

* update docs

* add mask param to rasterio provider

docs/source/plugins.rst

@@ -38,22 +38,22 @@ pygeoapi for easier maintenance of software updates.
    updates and package management
 
 
-Example: custom pygeoapi data provider
---------------------------------------
+Example: custom pygeoapi vector data provider
+---------------------------------------------
 
-Lets consider the steps for a data provider plugin (source code is located here: :ref:`data Provider`).
+Lets consider the steps for a vector data provider plugin (source code is located here: :ref:`data Provider`).
 
 Python code
 ^^^^^^^^^^^
 
-The below template provides a minimal example (let's call the file ``mycooldata.py``:
+The below template provides a minimal example (let's call the file ``mycoolvectordata.py``:
 
 .. code-block:: python
 
    from pygeoapi.provider.base import BaseProvider
 
-   class MyCoolDataProvider(BaseProvider):
-       """My cool data provider"""
+   class MyCoolVectorDataProvider(BaseProvider):
+       """My cool vector data provider"""
 
        def __init__(self, provider_def):
            """Inherit from parent class"""
@@ -91,7 +91,7 @@ The below template provides a minimal example (let's call the file ``mycooldata.
 
 
 For brevity, the above code will always return the single feature of the dataset.  In reality, the plugin
-developer would connect to a data source with capabilities to run queries and return relevant a result set,
+developer would connect to a data source with capabilities to run queries and return a relevant result set,
 as well as implement the ``get`` method accordingly.  As long as the plugin implements the API contract of
 its base provider, all other functionality is left to the provider implementation.
 
@@ -104,23 +104,23 @@ The following methods are options to connect the plugin to pygeoapi:
 
 **Option 1**: Update in core pygeoapi:
 
-- copy ``mycooldata.py`` into ``pygeoapi/provider``
+- copy ``mycoolvectordata.py`` into ``pygeoapi/provider``
 - update the plugin registry in ``pygeoapi/plugin.py:PLUGINS['provider']`` with the plugin's
-  shortname (say ``MyCoolData``) and dotted path to the class (i.e. ``pygeoapi.provider.mycooldata.MyCoolDataProvider``)
+  shortname (say ``MyCoolVectorData``) and dotted path to the class (i.e. ``pygeoapi.provider.mycoolvectordata.MyCoolVectorDataProvider``)
 - specify in your dataset provider configuration as follows:
 
 .. code-block:: yaml
 
    providers:
        - type: feature
-         name: MyCoolData
+         name: MyCoolVectorData
          data: /path/to/file
          id_field: stn_id
 
 
 **Option 2**: implement outside of pygeoapi and add to configuration (recommended)
 
-- create a Python package of the ``mycooldata.py`` module (see `Cookiecutter`_ as an example)
+- create a Python package of the ``mycoolvectordata.py`` module (see `Cookiecutter`_ as an example)
 - install your Python package onto your system (``python setup.py install``).  At this point your new package
   should be in the ``PYTHONPATH`` of your pygeoapi installation
 - specify in your dataset provider configuration as follows:
@@ -129,10 +129,61 @@ The following methods are options to connect the plugin to pygeoapi:
 
    providers:
        - type: feature
-         name: mycooldatapackage.mycooldata.MyCoolDataProvider
+         name: mycooldatapackage.mycoolvectordata.MyCoolVectorDataProvider
          data: /path/to/file
          id_field: stn_id
 
+BEGIN
+
+Example: custom pygeoapi raster data provider
+---------------------------------------------
+
+Lets consider the steps for a raster data provider plugin (source code is located here: :ref:`data Provider`).
+
+Python code
+^^^^^^^^^^^
+
+The below template provides a minimal example (let's call the file ``mycoolrasterdata.py``:
+
+.. code-block:: python
+
+   from pygeoapi.provider.base import BaseProvider
+
+   class MyCoolRasterDataProvider(BaseProvider):
+       """My cool raster data provider"""
+
+       def __init__(self, provider_def):
+           """Inherit from parent class"""
+
+           BaseProvider.__init__(self, provider_def)
+           self.num_bands = 4
+           self.axes = ['Lat', 'Long']
+
+       def get_coverage_domainset(self):
+           # return a CIS JSON DomainSet
+
+       def get_coverage_rangetype(self):
+           # return a CIS JSON RangeType
+
+       def query(self, bands=[], subsets={}, format_='json'):
+           # process bands and subsets parameters
+           # query/extract coverage data
+           if format_ == 'json':
+               # return a CoverageJSON representation
+               return {'type': 'Coverage', ...}  # trimmed for brevity
+           else:
+               # return default (likely binary) representation
+               return bytes(112)
+
+For brevity, the above code will always JSON for metadata and binary or CoverageJSON for the data.  In reality, the plugin
+developer would connect to a data source with capabilities to run queries and return a relevant result set,
+As long as the plugin implements the API contract of its base provider, all other functionality is left to the provider
+implementation.
+
+Each base class documents the functions, arguments and return types required for implementation.
+
+END
+
 Example: custom pygeoapi formatter
 ----------------------------------