Dunitz/db setup (#1619)

* initial database setup

server/db/cellxgene_orm.py

@@ -0,0 +1,60 @@
+from datetime import datetime
+
+from sqlalchemy import (
+    Column,
+    DateTime,
+    ForeignKey,
+    String,
+)
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import relationship
+
+Base = declarative_base()
+
+
+class CellxGeneUser(Base):
+    """
+    A registered CellxGene user.
+    Links a user to their annotations
+    """
+
+    __tablename__ = "cxguser"
+
+    id = Column(String, primary_key=True)
+    created_at = Column(DateTime, nullable=False, default=datetime.utcnow)
+    updated_at = Column(DateTime, nullable=False, default=datetime.utcnow, onupdate=datetime.utcnow)
+
+    # Relationships
+    annotations = relationship("Annotation", back_populates="cxguser")
+
+
+class Annotation(Base):
+    """
+    An annotation is a link between a user, a dataset and tiledb dataframe. A user can have multiple annotations for a
+    dataset, the most recent annotation (based on created_at) will be the default returned when queried
+    """
+
+    __tablename__ = "annotation"
+
+    id = Column(String, primary_key=True)
+    tiledb_uri = Column(String)
+    user_id = Column(String, ForeignKey("cxguser.id"), nullable=False)
+    dataset_id = Column(String, ForeignKey("cxgdataset.id"), nullable=False)
+    created_at = Column(DateTime, nullable=False, default=datetime.utcnow)
+
+    # Relationships
+    cxguser = relationship("CellxGeneUser", back_populates="annotations")
+    dataset = relationship("CellxGeneDataset", back_populates="annotations")
+
+
+class CellxGeneDataset(Base):
+    """
+    Datasets refer to cellxgene datasets stored in tiledb
+    """
+
+    __tablename__ = "cxgdataset"
+
+    id = Column(String, primary_key=True)
+    name = Column(String)
+    created_at = Column(DateTime, nullable=False, default=datetime.utcnow)
+    annotations = relationship("Annotation", back_populates="dataset")