Expose the head SEO function to be used in layouts

[adrienbaron]

This PR exposes the SEO head hook function as this.$nuxtI18nSeo on components.

This allows to disable seo head mixin on all components (by setting seo: false in nuxt i18n options).
Then it's possible to do this in your app layout (or wherever):

    head () {
      return this.$nuxtI18nSeo()
    },

This greatly improves performance as SEO links are not recomputed for every components but only for the layout itself.

This changes is not breaking as the default global registration with the same behaviour remains if seo: true in the configuration.

Resolves: #144

[paulgv]

Thanks @adrienbaron !
Could you also update the documentation to explain how to use the nuxtI18nSeo() method?

[adrienbaron]

@paulgv Done!
Btw thanks a lot to @manniL for his help on this, forgot to mention, and couldn't have done it without his help 👍

[manniL]

Happy we found a solution 🙊 (Also one that can be default at the next major version)

[kevinmarrec]

@adrienbaron @manniL Last commit on master seems to be related to this PR, and tests are not passing anymore, any ideas ? (CircleCI build fails)

[manniL]

@kevinmarrec Should be just the vue-ssr id(4eb03412:0). Will fix

[manniL]

@kevinmarrec fixed

[harmnot]

why $nuxtI18nSeo is not a function ??

[manniL]

@harmnot There hasn't been a release yet

[harmnot]

I was asking this https://cmty.app/nuxt/nuxt-i18n/issues/c176

[harmnot]

then, I try to find out, and follow the instruction https://github.com/nuxt-community/nuxt-i18n/blob/master/docs/seo.md here and after that , show the $nuxtI18nSeo is not a function

[paulgv]

Sorry for the delay, this wasn't released until recently in version 5.5.0: https://github.com/nuxt-community/nuxt-i18n/blob/master/CHANGELOG.md#550-2019-01-14