Limit compact index dependency parser to split on first colon

The upcoming compact index v2 format introduced by rubygems.org appends a
`created_at:ISO8601` field to each info line, and the timestamp's internal
colons were being treated as additional split delimiters. Splitting only on
the first colon keeps existing keys like `ruby:>= 2.7.0` intact while letting
multi-colon values pass through untouched.

rubygems/rubygems.org#6504

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: hsbt

lib/rubygems/resolver/api_set/gem_parser.rb

@@ -13,7 +13,7 @@ def parse(line)
   private
 
   def parse_dependency(string)
-    dependency = string.split(":")
+    dependency = string.split(":", 2)
     dependency[-1] = dependency[-1].split("&") if dependency.size > 1
     dependency[0] = -dependency[0]
     dependency

spec/bundler/compact_index_client/parser_spec.rb

@@ -47,7 +47,7 @@ def set_info_data(name, value)
   INFO
   let(:c_info) { <<~INFO }
     3.0.0 a:= 1.0.0,b:~> 2.0|checksum:ccc1,ruby:>= 2.7.0,rubygems:>= 3.0.0
-    3.3.3 a:>= 1.1.0,b:~> 2.0|checksum:ccc3,ruby:>= 3.0.0,rubygems:>= 3.2.3
+    3.3.3 a:>= 1.1.0,b:~> 2.0|checksum:ccc3,ruby:>= 3.0.0,rubygems:>= 3.2.3,created_at:2026-05-12T10:00:00Z
   INFO
 
   describe "#available?" do
@@ -195,7 +195,7 @@ def set_info_data(name, value)
           "3.3.3",
           nil,
           [["a", [">= 1.1.0"]], ["b", ["~> 2.0"]]],
-          [["checksum", ["ccc3"]], ["ruby", [">= 3.0.0"]], ["rubygems", [">= 3.2.3"]]],
+          [["checksum", ["ccc3"]], ["ruby", [">= 3.0.0"]], ["rubygems", [">= 3.2.3"]], ["created_at", ["2026-05-12T10:00:00Z"]]],
         ],
       ]
     end