chore!: improve decoding of required fields

A required field, confusingly, should probably be marked *optional* in
the protobuf. That way, we can throw errors when decoding. See [#252]
for more details.

This change:

- Updates `.proto` files to mark all required fields with our custom
  `required` tag
- Updates `.proto` files to mark most required fields as `optional`, so
  we can throw errors when decoding
- Throw errors when decoding if a field is missing

I tested this end-to-end.

[#252]: https://github.com/digidem/mapeo-schema/issues/252

proto/common/v1.proto

@@ -7,10 +7,10 @@ import "versionId/v1.proto";
 
 message Common_1 {
   // 32-byte random generated number
-  bytes docId = 1 [(required) = true];
+  optional bytes docId = 1 [(required) = true];
   repeated VersionId_1 links = 2;
-  google.protobuf.Timestamp createdAt = 3 [(required) = true];
-  google.protobuf.Timestamp updatedAt = 4 [(required) = true];
+  optional google.protobuf.Timestamp createdAt = 3 [(required) = true];
+  optional google.protobuf.Timestamp updatedAt = 4 [(required) = true];
   VersionId_1 originalVersionId = 5;
   bool deleted = 6 [(required) = true];
 }

proto/coreOwnership/v1.proto

@@ -13,12 +13,12 @@ message CoreOwnership_1 {
 
   Common_1 common = 1;
 
-  bytes authCoreId = 5;
-  bytes configCoreId = 6;
-  bytes dataCoreId = 7;
-  bytes blobCoreId = 8;
-  bytes blobIndexCoreId = 9;
-  CoreSignatures coreSignatures = 10;
+  optional bytes authCoreId = 5 [(required) = true];
+  optional bytes configCoreId = 6 [(required) = true];
+  optional bytes dataCoreId = 7 [(required) = true];
+  optional bytes blobCoreId = 8 [(required) = true];
+  optional bytes blobIndexCoreId = 9 [(required) = true];
+  CoreSignatures coreSignatures = 10 [(required) = true];
   bytes identitySignature = 11;
 
   message CoreSignatures {

proto/deviceInfo/v1.proto

@@ -21,6 +21,6 @@ message DeviceInfo_1 {
     selfHostedServer = 4;
   }
 
-  string name = 5;
+  optional string name = 5 [(required) = true];
   optional DeviceType deviceType = 6;
 }

proto/field/v1.proto

@@ -14,16 +14,16 @@ message Field_1 {
 
   Common_1 common = 1;
 
-  string tagKey = 5 [(required) = true];
+  optional string tagKey = 5 [(required) = true];
   enum Type {
     type_unspecified = 0;
     text = 1;
     number = 2;
     selectOne = 3;
     selectMultiple = 4;
   }
-  Type type = 6 [(required) = true];
-  string label = 7 [(required) = true];
+  optional Type type = 6 [(required) = true];
+  optional string label = 7 [(required) = true];
   enum Appearance {
     appearance_unspecified = 0;
     multiline = 1;

proto/icon/v1.proto

@@ -10,7 +10,7 @@ message Icon_1 {
   option (schemaName) = "icon";
 
   Common_1 common = 1;
-  string name = 2 [(required) = true];
+  optional string name = 2 [(required) = true];
 
   message IconVariantSvg {}
 
@@ -22,7 +22,7 @@ message Icon_1 {
       x3 = 3;
     }
 
-    PixelDensity pixelDensity = 1 [(required) = true];
+    optional PixelDensity pixelDensity = 1 [(required) = true];
   }
 
   message IconVariant {
@@ -43,8 +43,8 @@ message Icon_1 {
       int32 index = 2;
     }
 
-    Size size = 3 [(required) = true];
-    BlobVersionId blobVersionId = 4 [(required) = true];
+    optional Size size = 3 [(required) = true];
+    optional BlobVersionId blobVersionId = 4 [(required) = true];
   }
   repeated IconVariant variants = 3;
 }

proto/preset/v1.proto

@@ -15,15 +15,15 @@ message Preset_1 {
 
   Common_1 common = 1;
 
-  string name = 5;
+  optional string name = 5 [(required) = true];
   repeated Geometry geometry = 6;
   map<string, TagValue_1> tags = 7;
   map<string, TagValue_1> addTags = 8;
   map<string, TagValue_1> removeTags = 9;
   repeated FieldRef fieldRefs = 10;
   optional IconRef iconRef = 11;
   repeated string terms = 12;
-  string color = 13;
+  optional string color = 13 [(required) = true];
 
   enum Geometry {
     geometry_unspecified = 0;

proto/role/v1.proto

@@ -13,6 +13,6 @@ message Role_1 {
 
   Common_1 common = 1;
 
-  bytes roleId = 5;
-  uint32 fromIndex = 6;
+  optional bytes roleId = 5 [(required) = true];
+  optional uint32 fromIndex = 6 [(required) = true];
 }

proto/translation/v1.proto

@@ -13,10 +13,10 @@ message Translation_1 {
   Common_1 common = 1;
   DocRef docRef = 2;
 
-  string propertyRef = 3;
-  string languageCode = 4;
-  string regionCode = 5;
-  string message = 6;
+  optional string propertyRef = 3 [(required) = true];
+  optional string languageCode = 4 [(required) = true];
+  optional string regionCode = 5 [(required) = true];
+  optional string message = 6 [(required) = true];
 
   message DocRef {
     bytes docId = 1;