### Bug Description When packing a charm with a relation name containing a `.` in it, charmcraft packs it without any issue. However, when deploying to juju, it then fails complaining that this endpoints is not a valid field name. It fails with ``` $ juju deploy ./bug-charmcraft_amd64.charm ERROR Put https://localhost:40609/model-4a471354-e9b6-4232-8f73-bad9becf626b/charms/bug-charmcraft-3097777: cannot upload charm: invalid charm data: "dead.beef" is not a valid field name ``` I have the feeling a part of it should be in juju but I don't know how much, but also, charmcraft should be a bit stricter on the names. This [function](https://github.com/juju/juju/blob/3.6/mongo/utils/validfield.go#L15) checks what are valid field names or not. ### To Reproduce * Create a charm with one `requires` interface containing a `.` in it ``` requires: dead.beef: interface: deadbeef ``` ### Environment ``` $ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 24.04.3 LTS Release: 24.04 Codename: noble $ charmcraft version charmcraft 3.5.3 ``` ### charmcraft.yaml ```yaml type: charm name: bug-charmcraft title: Charm Template summary: A very short one-line summary of the charm. description: | A single sentence that says what the charm is, concisely and memorably. A paragraph of one to three short sentences, that describe what the charm does. A third paragraph that explains what need the charm meets. Finally, a paragraph that describes whom the charm is useful for. base: ubuntu@22.04 platforms: amd64: arm64: parts: charm: plugin: charm source: . requires: dead.beef: interface: deadbeef ``` ### Relevant log output ```shell ERROR Put https://localhost:40609/model-4a471354-e9b6-4232-8f73-bad9becf626b/charms/bug-charmcraft-3097777: cannot upload charm: invalid charm data: "dead.beef" is not a valid field name ```