feat: allow custom seed in fractional op (#136)

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## This PR
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- updates fractional schema to accept complex rules as first argument to
override targeting so that we can support using `cat` and other rules to
provide custom seeds to randomisation

### Related Issues
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open-feature/flagd#1264
resolves open-feature/flagd#1265

### Notes
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### Follow-up Tasks
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noted under this section -->
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### How to test
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see open-feature/flagd#1266

---------

Signed-off-by: Cole Bailey <[email protected]>
Signed-off-by: Kavindu Dodanduwa <[email protected]>
Co-authored-by: Kavindu Dodanduwa <[email protected]>

.github/workflows/pr-checks.yml

@@ -7,7 +7,7 @@ permissions:
   contents: read
 
 env:
-  GO_VERSION: 1.20.7
+  GO_VERSION: 1.22
 
 jobs:
   lint-protos:

json/targeting.json

@@ -486,7 +486,7 @@
       "items": [
         {
           "description": "Bucketing value used in pseudorandom assignment; should be unique and stable for each subject of flag evaluation. Defaults to a concatenation of the flagKey and targetingKey.",
-          "$ref": "#/$defs/varRule"
+          "$ref": "#/$defs/anyRule"
         },
         {
           "$ref": "#/$defs/fractionalWeightArg"

json/targeting.yaml

@@ -389,7 +389,7 @@ type: object
     - description: Bucketing value used in pseudorandom assignment; should be unique
         and stable for each subject of flag evaluation. Defaults to a concatenation
         of the flagKey and targetingKey.
-      $ref: "#/$defs/varRule"
+      $ref: "#/$defs/anyRule"
     - $ref: "#/$defs/fractionalWeightArg"
     - $ref: "#/$defs/fractionalWeightArg"
     additionalItems:

json/test/positive/custom-ops.json

@@ -14,7 +14,10 @@
       "defaultVariant": "wild",
       "targeting": {
         "fractional": [
-          { "var": "user.name" },
+          { "cat": [
+            { "var": "$flagd.flagKey" },
+            { "var": "user.name" }
+          ]},
           ["clubs", 25],
           ["diamonds", 25],
           ["hearts", 25],