Ingest different DRS formats

This PR is a significant rewrite of how we handle DRS file paths to allow us to ingest paths of a few different known DRS formats.

This involved:

• creating a new crate to handle just loading the different DRS types
• changing ingestion to load the different types and then convert them to our metadata format
• fix some funky issues with data-dir not behaving how it should
  • I also made it optional so not having it means that all datasets are ingested

.docker/drs_config.toml

@@ -6,14 +6,14 @@ drs_format = "cmip5"
 root_dir = ".docker/data/obs"
 drs_format = "custom"
 parts_dir = [
-    "activity",
+    "project",
     "product",
     "institute",
     "model",
     "experiment",
-    "frequency",
-    "modeling_realm",
-    "mip_table",
+    "time_frequency",
+    "realm",
+    "cmor_table",
     "ensemble",
     "version",
     "variable",