Add common dependency specification per group

• I have searched the issues of this repo and believe that this is not a duplicate.
• I have searched the FAQ and general documentation and believe that my question is not already covered.

Feature Request

It would be handy to have the option to define a common dependency specification for a group.

Instead of

[tool.poetry.group.private.dependencies]
package1 = [ { version = "^2.1.288", source = "PRIVATE_REPO" } ]
package2 = [ { version = "^0.7.0.64", source = "PRIVATE_REPO" } ]
package3 = [ { version = "^0.0.47", source = "PRIVATE_REPO" } ]

[tool.poetry.group.windows.dependencies]
package4 = [ { version = "^1.0.0", platform = "windows", source = "PRIVATE_REPO" } ]
package5 = [ { version = "^1.0.0", platform = "windows", source = "PRIVATE_REPO" } ]
package6 = [ { version = "^1.0.0", platform = "windows", source = "PRIVATE_REPO" } ]

Do this

[tool.poetry.group.private]
source = "PRIVATE_REPO"

[tool.poetry.group.private.dependencies]
package1 = "^2.1.288"
package2 = "^0.7.0.64"
package3 = "^0.0.47"

[tool.poetry.group.windows]
platform = "windows"
source = "PRIVATE_REPO"

[tool.poetry.group.windows.dependencies]
package4 = "^1.0.0"
package5 = "^1.0.0"
package6 = "^1.0.0"

Start by reviewing the requested TOML examples and the linked Poetry enhancement guidance. Define how group-level source and platform settings should apply to dependency entries, including expected interactions with existing inline specifications. Done means the feature is implemented with documented behavior and coverage for the private and Windows group examples.