config refactor (#1854)

* split out config

* add tests for base and app config, refactor client config out of app config

* refactor default config retrieval

* create config test class and helper functions

* move default_config into server to fix import issue

server/test/fixtures/dataset_config_outline.py

@@ -0,0 +1,37 @@
+f"""
+dataset:
+  app:
+    scripts: {scripts} #list of strs (filenames) or dicts containing keys
+    inline_scripts: {inline_scripts} #list of strs (filenames)
+
+    about_legal_tos: {about_legal_tos}
+    about_legal_privacy: {about_legal_privacy}
+
+    authentication_enable: {authentication_enable}
+
+  presentation:
+    max_categories: {max_categories}
+    custom_colors: {custom_colors}
+
+  user_annotations:
+    enable: {enable_users_annotations}
+    type: {annotation_type}
+    hosted_tiledb_array:
+      db_uri: {db_uri}
+      hosted_file_directory: {hosted_file_directory}
+    local_file_csv:
+      directory: {local_file_csv_directory}
+      file: {local_file_csv_file}
+    ontology:
+      enable: {ontology_enabled}
+      obo_location: {obo_location}
+
+  embeddings:
+    names: {embedding_names}
+    enable_reembedding: {enable_reembedding}
+
+  diffexp:
+    enable: {enable_difexp}
+    lfc_cutoff: {lfc_cutoff}
+    top_n: {top_n}
+"""