fix: Add short doc on the file system layout for this project

docs/structure.md

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+# Code Structure
+
+This document is only of use to people considering being part of our
+development community.
+
+# Code walkthrough
+
+This is a short description of the file layout for this project.
+
+## The Top Level
+
+The top level directory mostly has subdirectories where all the work
+is done, so this is mostly project management files, like python
+packaging.
+
+The primary directories are:
+
+* main/tests - Which contains all the test cases
+* main/docs - Which contains all the documentation
+* main/tm_admin - Which contains all of the code.
+
+## Makefiles
+
+Some directories have a Makefile. This is for automating tasks used by
+developers. This is common for generating documentation or the other
+files this project creates. Since Makefiles do dependency tracking, it
+reduces the amount of files that hace to be regenerated after a
+change.
+
+## Generated Files
+
+This project supports multiple language bindings. These are all
+configured by the YAML based confg file that defines the data
+structures. The *generator.py* program creates the output files from
+the config file. These
+
+For example for the users table:
+
+* users_class.py - A class that defines the data as a dictionary
+* users.proto.py - The protobuf file for gRPC
+* users_proto.py - A class for accessing protobuf messages
+
+## Adding A Table
+
+To add a new database table, create the directory for it, and then
+create the following 3 files. Rename *foo* of course.
+
+	tm_admin/foo/
+		-> api.py
+		-> foo.py
+		-> foo.yaml
+
+The *foo.yaml* file defines the data structure for accessing the
+database. It is required when adding a new table. The *foo.py* is the
+one that defines the *FooDB* class, which is the glue between postgres
+and this project. The *FooDB* class contains code for direct table
+management within the database.
+
+The *api.py* files ia an API for accessing the database for Tasking
+Manager style projects. This can be incorporated into a FastAPI or
+Flask backend.
+
+## Testing
+
+All the test cases in the *tests* directory can be run standalone
+while debugging them, or via *pytest* for github. Note that all test
+cases must support the asyncio API used in the rest of the code.
+
+## API Support
+
+Each table directory contains an *api.py* files, which is support code
+for a website backend. This lets the queries used to support the front
+end share code with the testsuite.