Add abstract contract for graphql processor

Allows developers to extend from this base class to customize how annotations are processed.

This is a complementary commit for issue: #71

library/src/main/kotlin/io/github/wax911/library/annotation/processor/contract/AbstractGraphProcessor.kt

@@ -0,0 +1,45 @@
+package io.github.wax911.library.annotation.processor.contract
+
+import io.github.wax911.library.annotation.GraphQuery
+import io.github.wax911.library.annotation.processor.fragment.FragmentPatcher
+import io.github.wax911.library.logger.core.AbstractLogger
+
+/**
+ * GraphQL annotation processor contract
+ *
+ * @property defaultExtension The default extension to use for looking up graphql files
+ * @property defaultDirectory The target directory to look in within `assetManager`
+ * @property logger A custom logger facade which should be used
+ * @property fragmentPatcher An optional fragment patcher
+ *
+ * @see FragmentPatcher
+ * @see AbstractLogger
+ */
+abstract class AbstractGraphProcessor {
+
+    internal abstract val defaultExtension: String
+    internal abstract val defaultDirectory: String
+    internal abstract val logger: AbstractLogger
+    internal abstract val fragmentPatcher: FragmentPatcher
+
+    /**
+     * Returns a pair of query or mutation name and graphql contents
+     */
+    abstract val graphFiles: Map<String, String>
+
+    /**
+     * Finds graphql content matching the value provided by [GraphQuery]
+     *
+     * @param annotations A collection of method annotation from an ongoing request
+     *
+     * @return GraphQL query in the form of [String] or null if the request method was not
+     * annotated with [GraphQuery] or if the no such file could be found
+     */
+    abstract fun getQuery(annotations: Array<out Annotation>): String?
+
+    /**
+     * Patch any query with fragment references, that don't already have the
+     * fragment defined with the query.
+     */
+    protected abstract fun patchQueries()
+}