Grafana Provider, with Data Source and Dashboard resources (#6206)

* Grafana provider

* grafana_data_source resource.

Allows data sources to be created in Grafana. Supports all data source
types that are accepted in the current version of Grafana, and will
support any future ones that fit into the existing structure.

* Vendoring of apparentlymart/go-grafana-api

This is in anticipation of adding a Grafana provider plugin.

* grafana_dashboard resource

* Website documentation for the Grafana provider.

vendor/github.com/rainycape/unidecode/unidecode.go

@@ -0,0 +1,58 @@
+// Package unidecode implements a unicode transliterator
+// which replaces non-ASCII characters with their ASCII
+// approximations.
+package unidecode
+
+//go:generate go run make_table.go
+
+import (
+	"sync"
+	"unicode"
+)
+
+const pooledCapacity = 64
+
+var (
+	slicePool    sync.Pool
+	decodingOnce sync.Once
+)
+
+// Unidecode implements a unicode transliterator, which
+// replaces non-ASCII characters with their ASCII
+// counterparts.
+// Given an unicode encoded string, returns
+// another string with non-ASCII characters replaced
+// with their closest ASCII counterparts.
+// e.g. Unicode("áéíóú") => "aeiou"
+func Unidecode(s string) string {
+	decodingOnce.Do(decodeTransliterations)
+	l := len(s)
+	var r []rune
+	if l > pooledCapacity {
+		r = make([]rune, 0, len(s))
+	} else {
+		if x := slicePool.Get(); x != nil {
+			r = x.([]rune)[:0]
+		} else {
+			r = make([]rune, 0, pooledCapacity)
+		}
+	}
+	for _, c := range s {
+		if c <= unicode.MaxASCII {
+			r = append(r, c)
+			continue
+		}
+		if c > unicode.MaxRune || c > transCount {
+			/* Ignore reserved chars */
+			continue
+		}
+		if d := transliterations[c]; d != nil {
+			r = append(r, d...)
+		}
+	}
+	res := string(r)
+	if l <= pooledCapacity {
+		slicePool.Put(r)
+	}
+	return res
+}