Resolve "add facets to openserach provider"

Closes #11 (closed)

finally I ended up with some remarks from mypy regarding missing child classes (getId and capabilites) and unexpected keywords for defined types:

mypy report

[{
	"resource": "/home/mathias/development/searchapi/sandbox/src/searchapi/opensearch_provider.py",
	"owner": "_generated_diagnostic_collection_name_#3",
	"code": {
		"value": "call-arg",
		"target": {
			"$mid": 1,
			"path": "/en/latest/_refs.html",
			"scheme": "https",
			"authority": "mypy.readthedocs.io",
			"fragment": "code-call-arg"
		}
	},
	"severity": 8,
	"message": "Unexpected keyword argument \"context\" for \"SearchResponse\"; did you mean \"@context\"?",
	"source": "Mypy",
	"startLineNumber": 84,
	"startColumn": 21,
	"endLineNumber": 87,
	"endColumn": 57,
	"origin": "extHost1"
},{
	"resource": "/home/mathias/development/searchapi/sandbox/src/searchapi/opensearch_provider.py",
	"owner": "_generated_diagnostic_collection_name_#3",
	"code": {
		"value": "call-arg",
		"target": {
			"$mid": 1,
			"path": "/en/latest/_refs.html",
			"scheme": "https",
			"authority": "mypy.readthedocs.io",
			"fragment": "code-call-arg"
		}
	},
	"severity": 8,
	"message": "Unexpected keyword argument \"service\" for \"SearchResult\"",
	"source": "Mypy",
	"startLineNumber": 113,
	"startColumn": 17,
	"endLineNumber": 124,
	"endColumn": 18,
	"origin": "extHost1"
},{
	"resource": "/home/mathias/development/searchapi/sandbox/src/searchapi/opensearch_provider.py",
	"owner": "_generated_diagnostic_collection_name_#3",
	"code": {
		"value": "call-arg",
		"target": {
			"$mid": 1,
			"path": "/en/latest/_refs.html",
			"scheme": "https",
			"authority": "mypy.readthedocs.io",
			"fragment": "code-call-arg"
		}
	},
	"severity": 8,
	"message": "Unexpected keyword argument \"language\" for \"SearchResult\"",
	"source": "Mypy",
	"startLineNumber": 113,
	"startColumn": 17,
	"endLineNumber": 124,
	"endColumn": 18,
	"origin": "extHost1"
},{
	"resource": "/home/mathias/development/searchapi/sandbox/src/searchapi/opensearch_provider.py",
	"owner": "_generated_diagnostic_collection_name_#3",
	"code": {
		"value": "index",
		"target": {
			"$mid": 1,
			"path": "/en/latest/_refs.html",
			"scheme": "https",
			"authority": "mypy.readthedocs.io",
			"fragment": "code-index"
		}
	},
	"severity": 8,
	"message": "Value of type \"Callable[[], Capabilities]\" is not indexable",
	"source": "Mypy",
	"startLineNumber": 142,
	"startColumn": 34,
	"endLineNumber": 142,
	"endColumn": 61,
	"origin": "extHost1"
},{
	"resource": "/home/mathias/development/searchapi/sandbox/src/searchapi/opensearch_provider.py",
	"owner": "_generated_diagnostic_collection_name_#4",
	"code": {
		"value": "W0223:abstract-method",
		"target": {
			"$mid": 1,
			"path": "/en/latest/user_guide/messages/warning/abstract-method.html",
			"scheme": "https",
			"authority": "pylint.readthedocs.io"
		}
	},
	"severity": 4,
	"message": "Method 'capabilities' is abstract in class 'SearchProvider' but is not overridden in child class 'OpensearchProvider'",
	"source": "Pylint",
	"startLineNumber": 18,
	"startColumn": 1,
	"endLineNumber": 18,
	"endColumn": 25,
	"origin": "extHost1"
},{
	"resource": "/home/mathias/development/searchapi/sandbox/src/searchapi/opensearch_provider.py",
	"owner": "_generated_diagnostic_collection_name_#4",
	"code": {
		"value": "W0223:abstract-method",
		"target": {
			"$mid": 1,
			"path": "/en/latest/user_guide/messages/warning/abstract-method.html",
			"scheme": "https",
			"authority": "pylint.readthedocs.io"
		}
	},
	"severity": 4,
	"message": "Method 'getid' is abstract in class 'SearchProvider' but is not overridden in child class 'OpensearchProvider'",
	"source": "Pylint",
	"startLineNumber": 18,
	"startColumn": 1,
	"endLineNumber": 18,
	"endColumn": 25,
	"origin": "extHost1"
}]