[FEAT] Review the Google Analytics configuration

[tbouffard]

See if we can implement exactly the following rules as described in https://docs.r-hub.io/#privacy (Hugo framework configuration)

[privacy.googleAnalytics]
anonymizeIP = true
disable = false
respectDoNotTrack = true
useSessionStorage = true

This means

• IP addresses are anonymized within Google Analytics,
• The GA templates respect the “Do Not Track” HTTP header,
• The use of Cookies is disabled, instead Session Storage to Store the GA Client ID is used.

The latest available configuration we use (at the time of writing this description) is

process-analytics.dev/gatsby-config.ts

Lines 56 to 75 in f17838b

	{
	resolve: `gatsby-plugin-google-gtag`,
	options: {
	trackingIds: [
	process.env.GATSBY_GA_MEASUREMENT_ID, // Google Analytics
	],
	// This object gets passed directly to the gtag config command
	gtagConfig: {
	// see https://www.gatsbyjs.com/plugins/gatsby-plugin-google-gtag/#the-gtagconfiganonymize_ip-option
	anonymize_ip: true,
	},
	// This object is used for configuration specific to this plugin
	pluginConfig: {
	// Puts tracking script in the head instead of the body
	head: false,
	// Google Global Site Tag will not be loaded at all for visitors that have “Do Not Track” enabled.
	respectDNT: true,
	},
	},
	},

2 rules described above (anonym_ip and respect DNT) are already configured but not "disable cookies".

If we can implement it, we can check if we can remove the decline/accept cookies or at least, show to users that we value their privacy.