schema: Describe object ID fields

Support describing ID fields of objects accepted by schemas.
Describe the issues introduced in v4.1 as having only one ID field to
allow KCIDB transition to multi-value IDs. The "version" field will be
added to issue's IDs in a following commit, once KCIDB is ready.

kcidb_io/schema/abstract.py

@@ -57,6 +57,13 @@ def __init__(cls, name, bases, _dict, **kwargs):
                        all(isinstance(e, str) for e in v)
                        for k, v in cls.graph.items())
             assert "" in cls.graph
+            assert isinstance(cls.id_fields, dict)
+            assert set(cls.graph) - {""} == set(cls.id_fields)
+            assert all(isinstance(fields, dict) and
+                       len(fields) > 0 and
+                       all(isinstance(n, str) and isinstance(t, type)
+                           for n, t in fields.items())
+                       for fields in cls.id_fields.values())
 
     def __str__(cls):
         return f"v{cls.major}.{cls.minor}"
@@ -133,6 +140,8 @@ class Version(ABC, metaclass=MetaVersion):
     # list of the same, with the empty string mapping to a list of topmost
     # object list names.
     graph = None
+    # A map of object names and dictionaries of their ID fields and types
+    id_fields = None
 
     @classmethod
     @abstractmethod

kcidb_io/schema/test_abstract.py

@@ -15,12 +15,14 @@ class V1(Version):
             minor = 0
             json = dict(title="v1")
             graph = {"": []}
+            id_fields = {}
 
         class V2(V1):
             major = 2
             minor = 0
             json = dict(title="v2")
             graph = {"": []}
+            id_fields = {}
 
             @staticmethod
             def _inherit(data):
@@ -31,12 +33,14 @@ class V2D1(V2):
             minor = 1
             json = dict(title="v2.1")
             graph = {"": []}
+            id_fields = {}
 
         class V3(V2D1):
             major = 3
             minor = 0
             json = dict(title="v3")
             graph = {"": []}
+            id_fields = {}
 
             @staticmethod
             def _inherit(data):
@@ -138,12 +142,14 @@ class V1(Version):
             minor = 0
             json = dict(title="v1")
             graph = {"": []}
+            id_fields = {}
 
         class V2A(V1):
             major = 2
             minor = 0
             json = dict(title="v2a")
             graph = {"": []}
+            id_fields = {}
 
             @staticmethod
             def _inherit(data):
@@ -154,6 +160,7 @@ class V2B(V1):
             minor = 0
             json = dict(title="v2b")
             graph = {"": []}
+            id_fields = {}
 
             @staticmethod
             def _inherit(data):

kcidb_io/schema/v01_01.py

@@ -579,6 +579,12 @@ class Version(AbstractVersion):
         "builds": ["tests"],
         "tests": []
     }
+    # A map of object names and dictionaries of their ID fields and types
+    id_fields = dict(
+        revisions=dict(origin=str, origin_id=str),
+        builds=dict(origin=str, origin_id=str),
+        tests=dict(origin=str, origin_id=str),
+    )
 
     @classmethod
     def _get_version(cls, data):

kcidb_io/schema/v02_00.py

@@ -549,6 +549,13 @@ class Version(PreviousVersion):
         "tests": []
     }
 
+    # A map of object names and dictionaries of their ID fields and types
+    id_fields = dict(
+        revisions=dict(id=str),
+        builds=dict(id=str),
+        tests=dict(id=str),
+    )
+
     @classmethod
     def _get_version(cls, data):
         """

kcidb_io/schema/v04_00.py

@@ -690,6 +690,13 @@ class Version(PreviousVersion):
         "tests": []
     }
 
+    # A map of object names and dictionaries of their ID fields and types
+    id_fields = dict(
+        checkouts=dict(id=str),
+        builds=dict(id=str),
+        tests=dict(id=str),
+    )
+
     @staticmethod
     def _inherit(data):
         """

kcidb_io/schema/v04_01.py

@@ -898,3 +898,12 @@ class Version(PreviousVersion):
         "issues": ["incidents"],
         "incidents": [],
     }
+
+    # A map of object names and dictionaries of their ID fields and types
+    id_fields = dict(
+        checkouts=dict(id=str),
+        builds=dict(id=str),
+        tests=dict(id=str),
+        issues=dict(id=str),
+        incidents=dict(id=str),
+    )