…anagement with an abstract unit system (nicolas-grekas, hhamon, gharlan)This PR was merged into the 5.0-dev branch.Discussion----------[String] a new component for object-oriented strings management with an abstract unit system| Q             | A| ------------- | ---| Branch?       | master| Bug fix?      | no| New feature?  | yes| Deprecations? | no| Tickets       | -| License       | MIT| Doc PR        | -This is a reboot of#22184 (thanks@hhamon for working on it) and a generalization of my previous work on the topic ([patchwork/utf8](https://github.com/tchwork/utf8)). Unlike existing libraries (including `patchwork/utf8`), this component provides a unified API for the 3 unit systems of strings: bytes, code points and grapheme clusters.The unified API is defined by the `AbstractString` class. It has 2 direct child classes: `BinaryString` and `AbstractUnicodeString`, itself extended by `Utf8String` and `GraphemeString`.All objects are immutable and provide clear edge-case semantics, using exceptions and/or (nullable) types!Two helper functions are provided to create such strings:```phpnew GraphemeString('foo') == u('foo'); // when dealing with Unicode, prefer grapheme unitsnew BinaryString('foo') == b('foo');````GraphemeString` is the most linguistic-friendly variant of them, which means it's the one ppl should use most of the time *when dealing with written text*.Future ideas: - improve tests - add more docblocks (only where they'd add value!) - consider adding more methods in the string API (`is*()?`, `*Encode()`?, etc.) - first class Emoji support - merge the Inflector component into this one - use `width()` to improve `truncate()` and `wordwrap()` - move method `slug()` to a dedicated locale-aware service class - propose your ideas (send PRs after merge)Out of (current) scope: - what [intl](https://php.net/intl) provides (collations, transliterations, confusables, segmentation, etc)Here is the unified API I'm proposing in this PR, borrowed from looking at many existing libraries, but also Java, Python, JavaScript and Go.```phpfunction __construct(string $string = '');static function unwrap(array $values): arraystatic function wrap(array $values): arrayfunction after($needle, bool $includeNeedle = false, int $offset = 0): self;function afterLast($needle, bool $includeNeedle = false, int $offset = 0): self;function append(string ...$suffix): self;function before($needle, bool $includeNeedle = false, int $offset = 0): self;function beforeLast($needle, bool $includeNeedle = false, int $offset = 0): self;function camel(): self;function chunk(int $length = 1): array;function collapseWhitespace(): selffunction endsWith($suffix): bool;function ensureEnd(string $suffix): self;function ensureStart(string $prefix): self;function equalsTo($string): bool;function folded(): self;function ignoreCase(): self;function indexOf($needle, int $offset = 0): ?int;function indexOfLast($needle, int $offset = 0): ?int;function isEmpty(): bool;function join(array $strings): self;function jsonSerialize(): string;function length(): int;function lower(): self;function match(string $pattern, int $flags = 0, int $offset = 0): array;function padBoth(int $length, string $padStr = ' '): self;function padEnd(int $length, string $padStr = ' '): self;function padStart(int $length, string $padStr = ' '): self;function prepend(string ...$prefix): self;function repeat(int $multiplier): self;function replace(string $from, string $to): self;function replaceMatches(string $fromPattern, $to): self;function slice(int $start = 0, int $length = null): self;function snake(): self;function splice(string $replacement, int $start = 0, int $length = null): self;function split(string $delimiter, int $limit = null, int $flags = null): array;function startsWith($prefix): bool;function title(bool $allWords = false): self;function toBinary(string $toEncoding = null): BinaryString;function toGrapheme(): GraphemeString;function toUtf8(): Utf8String;function trim(string $chars = " \t\n\r\0\x0B\x0C\u{A0}\u{FEFF}"): self;function trimEnd(string $chars = " \t\n\r\0\x0B\x0C\u{A0}\u{FEFF}"): self;function trimStart(string $chars = " \t\n\r\0\x0B\x0C\u{A0}\u{FEFF}"): self;function truncate(int $length, string $ellipsis = ''): self;function upper(): self;function width(bool $ignoreAnsiDecoration = true): int;function wordwrap(int $width = 75, string $break = "\n", bool $cut = false): self;function __clone();function __toString(): string;````AbstractUnicodeString` adds these:```phpstatic function fromCodePoints(int ...$codes): self;function ascii(array $rules = []): self;function codePoint(int $index = 0): ?int;function folded(bool $compat = true): parent;function normalize(int $form = self::NFC): self;function slug(string $separator = '-'): self;```and `BinaryString`:```phpstatic function fromRandom(int $length = 16): self;function byteCode(int $index = 0): ?int;function isUtf8(): bool;function toUtf8(string $fromEncoding = null): Utf8String;function toGrapheme(string $fromEncoding = null): GraphemeString;```Case insensitive operations are done with the `ignoreCase()` method.e.g. `b('abc')->ignoreCase()->indexOf('B')` will return `1`.For reference, CLDR transliterations (used in the `ascii()` method) are defined here:https://github.com/unicode-org/cldr/tree/master/common/transformsCommits-------dd8745a [String] add more tests82a0095 [String] add tests012e92a [String] a new component for object-oriented strings management with an abstract unit system